Monarch Watch Monarch Watch

Western Monarchs

6 January 2022 | Author: Chip Taylor

My father was a Certified Public Accountant, and had I demonstrated a facility for numbers, I might have become a CPA as well. Instead, I became a biologist which I naively assumed would mean that I wouldn’t have to work with numbers – at least not a lot. As it turns out, understanding monarchs, or more accurately, attempting to understand monarchs, requires a lot of number crunching. But that only works if we have some numbers to work with, and if the numbers are reasonably accurate, which brings me to a monarch puzzle. Namely, how did the Western monarch population grow from an overwintering number of 1,914 in 2020 to over 200,000 in 2021? Both numbers are based on Xerces sponsored Thanksgiving Day Counts. Each count involves an examination and estimation of the number of monarchs at 261 known overwintering locations and the search for new sites which are often on private land. At many sites, the number of monarchs is so low, the count is an actual count rather than an estimate. That was mostly the case last year and the Thanksgiving number was followed by an end of the year accounting that produced only 1049 monarchs. The decline from 1914 to 1049 was not unexpected. From the end of a breeding season in September and October (depending on location), the population declines until the end of the first reproductive period in April.

So, from a January number of 1049, how many females would we expect to be alive in March at the beginning normal reproduction in California? We can expect attrition to continue from January to March, but let’s assume that 70% survive. That’s probably high, but let’s go with it. That leaves 734 individuals. Since the sex ratio shifts in Mexico from being dominated by males at the beginning of the winter season to being female dominated at the end of the season, let’s assume that applies to these numbers. At best, that would mean that 55-65% of the survivors would be females. Let’s say it’s 60%, or 441 females. The next question is – Is it possible for 441 females to produce a population of 200,000 monarchs in 3-4 generations? I don’t think so. I’ve done the math several times, and you can as well*. So, if we can’t see a way to account for a fall population of 200,000 from the overwintering numbers, it means we are missing something, and the next question is what could that be? There seem to be three possibilities, 1) monarchs originating from Mexico recolonized the breeding areas in the West in March and April, 2) there were thousands of overwintering monarchs that clustered at sites that have never been discovered or 3) that some monarchs that breed along the coast during the winter months responded to seasonal cues in March and moved inland where they gave rise to a first generation of monarchs that colonized the summer breeding ranges in the West, particularly those areas to the east and north of California.

To determine if there is any support for the idea that the West was recolonized by monarchs from Mexico, I examined the first sightings records posted to Journey North and all the images of monarchs posted to iNaturalist for March and April. There is nothing on either site that supports the hypothesis that monarchs returned from Mexico in good numbers this past spring. If they did, this influx was missed by all those who are inclined to report monarch sightings.

The possibility that there are coastal or even inland overwintering sites in California that have never been discovered is real. New sites are discovered from time to time. Given the length of the coastal area, and the possibility that some areas are relatively inaccessible, there is the possibility that thousands of monarchs overwintered at locations that weren’t part of the surveys in 2020. There are reasons to think that the conditions for establishing overwintering clusters were different in 2020. The mean temperatures in California for both September and October 2020 were the highest in the record. October was +6.7F above the long-term average. It is during these months that monarchs migrate toward the coast with numbers beginning to show up at the overwintering sites in mid-October. Monarchs don’t migrate when the temperatures are in the 90s and often not when in the mid 80s. Rather, they seek cooler sites. This behavior might have led them to cluster in atypical locations. Under these conditions, monarchs that are unable to avoid extreme high temperatures often become reproductive and drop out of the migration. Both of these things could have happened in September-October 2020. Although it’s possible, even likely, that there are alternative overwintering sites in California, there is simply no evidence that such sites played a role in the number of monarchs that survived the winter in 2020-2021.

The third explanation, that offspring of winter breeding monarchs moved inland to reproduce in March and April is a possibility but, again, there is no precedent for such an occurrence. However, given the widespread reproduction this past winter reported to the Monarch Larval Monitoring Project (view summary of California data by year), this possibility shouldn’t be discounted. The fact is, we know little about the population dynamics of monarchs that reproduce during the winter months in California. So, what is the possibility that some recently emerged offspring of coastal breeding monarchs do move inland in March to reproduce? To answer that question, we need to know how monarchs respond to seasonal cues that might initiate migratory behavior. To dive into that topic, let’s look at the daylength/celestial conditions that occur during the migration northward in Mexico to see if they apply to California. We know that mating increases at the overwintering sites in Mexico in mid-February after the sun angle at solar noon (SASN) increases to 57 degrees. The date of the migration northward from the colonies is temperature dependent but usually starts around the 1st of March. The SASN at that time is 63 degrees. The possibility that the northward migration from Mexico is associated changes in the SASN is supported by the graphic (Fig 1) David Gibo and I put together based on first sightings assembled by Elizabeth Howard and her team at Journey North years ago**. The 63 SASN for a beginning of the departure from Mexico doesn’t seem to match a tracking of 56 SASN once the monarchs reach Texas. However, it is possible that the cues to leave actually began weeks earlier when the SASN reached 56 or 57 degrees. Preparing for departure from the colonies may in fact take several weeks since it is still cool at the Mexican sites, especially at night, which could delay the physiological and behavioral responses to the changing conditions. Once monarchs leave the overwintering colonies, they encounter consistently higher temperatures and move northward about 50-55 miles a day, which is faster than the pace of the SASN in degrees. The SASN advances about one degree, or 69 miles, every three days***. The difference in the respective paces allows the butterflies to soon track an SASN of 56 degrees – if the weather allows.

As to prepping to leave the coastal areas for the interior, cool conditions along the coast and the nearby foothills could result in a delay in physiological and behavioral development and could determine when monarchs move inland. It may help, when thinking of these dynamics, to remember that overwintering monarchs have a low metabolic rate which increases once they respond sufficiently to seasonal conditions to become reproductive. Further, when thinking about the possibility that breeding monarchs along the coast might move inland, that may only apply to newly emerged monarchs that have yet to become reproductive. From all we have been able to ascertain, once late summer monarchs become reproductive, they do not migrate even if exposed to seasonal changes that result in migration by younger cohorts. In effect, once reproductive, older adults appear to be insensitive or “blind” to seasonal cues. Mating is delayed in monarchs with most mating occurring on days 3-5 post emergence. That coincides with ovary development and the production of juvenile hormone. My guess is that the conditions experienced during these first 3-5 days determine whether monarchs migrate. If I’m correct, newly emerged monarchs that result from continuous breeding along the coast, if exposed to seasonal cues that signal migration, would do so. There is no a priori reason to expect that that would not happen. Still, there are reasons to be skeptical about whether this scenario played out last March and April. We know too little about winter breeding along the coast. We need to know the where and when new adults are produced as well as their numbers.

Some may also wonder whether conditions seen in Mexico apply to California. They probably do. The following is a summary of the first day that the SASN reaches 56 degrees in California locations along with cities in Texas and Oklahoma. These dates and latitudes are represented in Fig. 1. These comparisons suggest that, at least in terms of daylength associated celestial cues, Western and Eastern monarchs are exposed to similar conditions.

Table 1. March dates SASN reaches 56 degrees in California, Texas and Oklahoma

Date	Location 1	Location 2
17 March	San Diego, CA (32°42'56")	Dallas, TX (32°48'20")
21 March	Ventura, CA (34°15'17")	Ardmore, OK (34°9'9")
23 March	Pismo Beach, CA (35°9'12")	Okmulgee, OK (35°38'5")
27 March	Pacific Grove, CA (36°37'13")	Enid, OK (36°24'8")

Figure 1. A few monarchs from Mexico appear to reach Texas during the first week of March when the SASN is close to 56 degrees. As monarchs continue to arrive from Mexico and move further north in Texas and into Oklahoma, they appear to be tracking an SASN of 56 until the third week of April. By that date, most have died and there is a drop in sightings until the first-generation monarchs begin moving north in late April and May.

Conclusion

So, how can we explain the difference in the overwintering numbers from 2020 to 2021? Two things seem unlikely. It doesn’t seem possible that the few hundred females that survived from last year’s overwintering population could account for over 200,000 monarchs this year. Nor is there any evidence that monarchs arrived in the inner West in March and April from Mexico. That leaves us with the possibility that there were unfound overwintering sites with thousands, perhaps 10’s of thousands of monarchs, and the possibility that offspring of coastal breeding monarchs moved inland and generated a first generation that colonized the breeding areas in the inner West and the northwestern states. The problem is there is no evidence for either – although both may have occurred. There is at least one other approach. We can use what is known about monarch population dynamics to bracket the possible number of females it took to produce more than 200,000 adults – a lot more in fact – since we need to account for attrition during the migration. Those calculations will have to wait until we get the final numbers, but see the notes below.

Notes

*Here are a few of the details that are required to calculate population increases. First, you have to know, or estimate, the number of females at the start of a generation. Then, you need to estimate the mean number of eggs produced per female (250-350). That is followed by an estimate of the survival to the pupal stage (0.01 or more) and then the survival of pupae to adult (0.76). Since not all adults reproduce, you need another estimate of those numbers (0.85). The last multiplier is the proportion of females which is generally close to 0.45.

Here is an example calculation:

1000 x 250 = 250,000 x 0.01 = 2500 x 0.76 = 1900 x 0.85 = 1615 x 0.45 = 727. Hmmm, those numbers don’t work since you end up with fewer females than we started with. If we increase the egg to pupal survival to 0.03 we get the following.

1000 x 250 = 250,000 x 0.03 = 7500 x 0.76 = 5700 x 0.85 = 4845 x 0.45 = 2180. That yields a 2.2-fold increase. Even after 4 generations that rate of increase isn’t sufficient to generate more than 200,000 migrants.

Perhaps I’m missing something or underestimating egg numbers or survival, but if these calculations are even close, they suggest that thousands of females were required to produce this year’s overwintering numbers. That said, we haven’t accounted for the attrition during the migration made by the first generation as it moves into the inner west and the northwestern states. Two things could happen. The number of females surviving to reproduce would be reduced, and the mean number of eggs per female would decline as well, not only due to a reduction in the size of the cohort, but because the search time for host plants is likely to increase, especially in the West. If there is either a significant loss of the first-generation females during colonization or significant reduction in mean egg number, it would be difficult for the population to produce an overwintering population of >200K. The keys to population growth are the number of females at the start of each generation and, in the case of monarchs West and East, the size of the first generation and its success in reaching the main summer breeding grounds. Again, those considerations suggest that a relatively large number of females had to be involved in the establishment of the first-generation last year.

The calculations I’ve used assume constant rates of mortality from one generation to the next. However, the incidence of parasitism by tachinid flies and O. e. tends to increase as the season progresses. Such increases would reduce both the proportion of larvae reaching the pupal stage and surviving to the adult stage. In the case of the adults with O. e., their fitness to reproduce would be compromised. We also need to recognize that realized fecundity, i.e., the mean eggs per female per generation, varies with temperature, nectar availability, and the distribution, abundance and quality of milkweeds. These factors also affect population growth.

** In subsequent years, especially in 2012 and 2017, it became apparent that high March temperatures and strong southwesterly winds allowed monarchs to advance much faster than expected for SASN. It was cooler in March in Texas from 1997 to 2000 than it has been in recent years.

*** Actually, the SASN advance averages less than 69 miles per day over the entire migration, but three days per degree of latitude is a useful reference point for discussion.

Relevant literature

Altizer, S., Oberhauser, K. S., and L.P. Brower. 2000. Associations between host migration and the prevalence of a protozoan parasite in natural populations of monarch butterflies Ecological Entomology 25(2):125 – 139 DOI:10.1046/j.1365-2311.2000.00246.x

Brower, L.P. and R.M. Pyle. 2004. The interchange of migratory monarchs between Mexico and the Western United States, and the importance of floral corridors in the fall and spring migrations. In Conserving Migratory Pollinators and Nectar Corridors in Western North America, edited by G. Nabhan, 144-166. Tucson: University of Arizona Press.

Grant, T. J., D. T. T. Flockhart, T. R. Blader, R. L. Hellmich, G. M. Pitman, S. Tyner, D. R. Norris, and S. P.Bradbury. 2020. Estimating arthropod survival probability from field counts: a case study with monarch butterflies. Ecosphere 11(4):e03082. 10.1002/ecs2.3082

James, D.G.; Schaefer,M.C.; Krimmer Easton, K.; Carl, A. First Population Study on Winter Breeding Monarch Butterflies, Danaus plexippus (Lepidoptera: Nymphalidae) in the Urban South Bay of San Francisco, California. Insects 2021, 12, 946. https://doi.org/10.3390/ insects12100946

Nail, K. R., C. Stenoien, and K. S. Oberhauser. 2015. Immature monarch survival: effects of site characteristics, density, and time. Annals of the Entomological Society of America 108:680–690.

Oberhauser, K., R. Wiederholt, J. E. Diffendorfer, D.Semmens, L. Ries, W. E. Thogmartin, L. Lopez-Hoffman, and B. Semmens. 2017. A trans-nationalmonarch butterfly population model and implica-tions for regional conservation priorities. EcologicalEntomology 42:51–60.

Semmens, B. X., D. J. Semmens, W. E. Thogmartin, R.Wiederholt, L. Lopez-Hoffman, J. E. Diffendorfer, J.M. Pleasants, K. S. Oberhauser, and O. R. Taylor.2016. Quasi-extinction risk and population targets for the Eastern, migratory population of monarch butterflies (Danaus plexippus). Scientific Reports6:23265.

Taylor OR Jr, Lovett JP, Gibo DL, Weiser EL, Thogmartin WE, Semmens DJ, Diffendorfer JE, Pleasants JM, Pecoraro SD and Grundel R (2019) Is the Timing, Pace, and Success of the Monarch Migration Associated With Sun Angle? Front. Ecol. Evol. 7:442. doi: 10.3389/fevo.2019.0044

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How many hectares in 2021-2022?

6 January 2022 | Author: Chip Taylor

Each year, at about this time, I administer a test – to myself. I have one question. How big, in term of hectares*, will the overwintering population be this year? Technically, I fail the test every time and expect to. Realistically, it would be virtually impossible to correctly predict the overwintering numbers given the number of variables involved in each migration. For example, there is no way to predict the weather conditions in Mexico that determine how tightly the monarchs are clustered when measured during mid-December. There are other variables in Mexico as well – such as the density of the forest. What I’m alluding to is that a hectare in one part of the forest could represent a widely different number of monarchs from a hectare in another location. So, the bottom line is that everything is an estimate, and we don’t know how well the hectares from one year compare to those of another. While that is true, the hectare measure seems to represent the size of the population fairly well. For example, the number of monarchs tagged in the Midwest each fall is strongly correlated with the overwintering number. That would not be true if there was a lot of error in the number of hectares and the number of butterflies per hectare following each migration.

So, if the number of tagged butterflies can be used to predict the overwintering population, why don’t I just use those numbers as predictors? Unfortunately, it takes months and months to assemble all the tagging records for a given year. Therefore, I have to look to other measures or conditions and draw on the historical record to arrive at a prediction. The conditions during the spring in Texas, the recolonization of the northern breeding areas in May, the summer temperatures, the weather during the migration and the availability of nectar sources in Texas all differ from year to year and all factor into the number of monarchs that reach the overwintering sites. The challenge for me is to assess each of these conditions for a given year and to compare these outcomes with the record that goes back to 1994.

After considering all of these factors for this past season, I came up with the following estimate – 0.8-1.2 hectares. Ouch! That’s low and lower than the 2.01 hectares measured last year. In fact, if 1.2 hectares this year, that would be the lowest number since the winter of 2014-2015. I know that that is not what anyone wants to hear, and I don’t want to accept those numbers myself, but that is what my assessment tells me. My history with these estimates is fair, but I usually underestimate the size of the population which means that I’m overestimating the negative impact of one or more factors. These over and under estimates speak to my goal which is to develop a deep understanding of all the factors that determine the size of the population. Being wrong goes along with learning how to refine my estimates. Last year my estimate for the hectare total was almost spot on – 2.0 hectares vs a measured 2.01 hectares. It was more of a guess than a data-based prediction, but I’ll take credit for being close. There are reasons to think I will be close again this year and other reasons to predict that the number will be higher.

In the following paragraphs I’ll summarize the reasons for why my prediction might be right or wrong. Although I evaluate data from the entire range of the eastern monarch range, my prediction is largely based on what I can glean about the colonization and population growth that occurs from 90-100W – a region from just west of Madison, WI to the central Dakotas. Tagging results indicate that about 70% of the monarchs that reach the overwintering sites originate from this region.

There are several reasons the monarch numbers at the overwintering sites might be lower this winter than in recent years. First, as shown in the drought monitor images for this past summer (Figs 1-3), there was a severe drought in the Dakotas that extended eastward well into Minnesota. Droughts have a strong negative impact on monarch population development since plant growth is stunted, plant quality declines and nectar is more limited. These conditions decrease monarch longevity and reproductive success. High temperatures, which often accompany drought conditions, also negatively influence population growth. This year, the first sightings posted to Journey North indicated that monarchs arrived in the northern breeding areas on time and in good numbers. However, post arrival, the regional and state temperatures were substantially above the long-term averages for June through August. For example, the average temperatures were +3.1F for the Upper Midwest, +1.2F of the Ohio Valley and +2.8F for the Northeast. The temperatures in the states in the drought areas were +4.3 for North Dakota, +3.9 for South Dakota and +3.8F for Minnesota. The temperature for Minnesota was the second highest since 1895. The temperatures are significant since the record shows that populations decline when the mean temperatures exceed +2F. These above average temperatures persisted into September in the Upper Midwest and the effect was to delay the migration. Again, the tagging data shows that late migrations are associated with lower numbers reaching the overwintering sites.

As to numbers in the migration, Journey North tallies the number of roosts reported by observers. These sightings include estimates of the number of monarchs. A quick scan of these estimates suggested that the numbers for all sightings this year were about half those in 2020. The observations by Harlen and Altus Aschen near Port Lavaca, TX suggested that the flow of monarchs along the Gulf coast, many of which probably originated from the Northeast, was late and involved a relatively small number of monarchs.

In summary, all of the metrics used to assess the size of the summer and migratory populations indicated that the population reaching the overwintering sites would be substantially lower than the number measured in 2020.

There are also reasons why my estimates might be overly pessimistic. A recent report from El Rosario offered that the population this year was about a third larger than last year. Further, in early December, the counts of trees occupied by monarchs at Chincua, Cerro Pelon and Herrada were all greater than I would have expected based on my assessments. We will have to wait for the official counts. I’d be delighted to be wrong – on the low side that is.

*One hectare is equal to 2.47 acres. One acre is approximately the area of a football field exclusive of the end zones.

Figure 1. June Drought Monitor

Figure 2. July Drought Monitor

Figure 3. August Drought Monitor

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2021 year-end summary

31 December 2021 | Author: Jim Lovett

Season’s Greetings from the staff at Monarch Watch!

We would like to thank everyone who contributed to our program in the last year. That support has enabled us to maintain and grow our programs and aid many people in their efforts to create habitats for monarchs. As you know, sustaining the migration is a massive undertaking due to continuing loss of milkweed/monarch habitats. We’ve distributed over one million plants through our Milkweed Market and free milkweeds programs since 2014 but we need to do more. We expanded our efforts in California this past season and distributed about 3,800 plugs of Asclepias fascicularis, the most common hostplant used by monarchs in that state. Our ambitious goal for California in 2022 is the distribution of at least 36,000 milkweed plugs. We will be working with other non-governmental organizations as well as state and federal agencies to find homes for these milkweeds.

Although adjustments to Covid-19 continued with the cancelation of our Spring and Fall Open House events this year, we were able to hold our fall tagging event at the Baker Wetlands to the delight of many families. We had a wonderful day in the great outdoors and there were smiles all around.

The newly developed Monarch Watch mobile app will make it easier for many taggers to record butterflies as they are tagged and submit data electronically. The beta testing of the app has gone well, and we hope to launch it for general use during the 2022 tagging season. We will have much more to say about this in the coming months. As we mentioned last year, two papers have been published recently on the results of the tagging. The data analysis is continuing and two additional papers are well underway. It’s a slow process – lots of data!

This past year, to expand our ability to distribute more milkweeds for restoration projects, we worked closely with the KU Endowment Association to raise funds through the annual “One Day. One KU.” campaign held in February. Hundreds of people responded with contributions sufficient to enable us to distribute an additional 28,000 milkweed plugs and clearly demonstrated the widespread support for monarch and pollinator conservation.

Time flies when you are having fun and that’s also true if you have a vision and a mission and are driven to see it through. That may be fairly said of the Monarch Watch team. Although we often wondered if we would survive financially from one year to the next, Monarch Watch continued to grow and will be celebrating 30 years of education, conservation, and research in 2022! We are not yet sure how we will mark this milestone, but there will certainly be a retrospective component and maybe an event or two. We will keep you informed via our blog, email updates, and social media.

Again, thank you for your continued support and we hope you will be with us again this coming year. Best wishes to you and yours for a happy and healthy holiday season. Please stay safe!

Sincerely,

Chip Taylor, Jim Lovett, Ann Ryan, Angie Babbit and Dena Podrebarac
Team Monarch Watch

To keep up with the status of monarchs and other news, subscribe to our email updates ( monarchwatch.org/subscribe ), join our email discussion list ( monarchwatch.org/dplex ), visit our blog ( monarchwatch.org/blog ) and follow us on Facebook, Instagram, and Twitter.

Monarch Watch
Kansas Biological Survey & Center for Ecological Research
University of Kansas
2021 Constant Avenue
Lawrence, KS 66047
785-864-4441
monarch@ku.edu
monarchwatch.org

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Monarch Watch Update August 2021

23 August 2021 | Author: Jim Lovett

This newsletter was recently sent via email to those who subscribe to our email updates. If you would like to receive periodic email updates from Monarch Watch, please take a moment to complete and submit the short Google Form at https://monarchwatch.org/subscribe/

Greetings!

Included in this issue:
1. Monarch Population Status
2. Monarch Watch Tagging Kits
3. Submitting Tag Data
4. Chip in for Monarch Watch
5. Monarch Waystations
6. Upcoming Monarch Watch Events
7. About This Monarch Watch List

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1. Monarch Population Status —by Chip Taylor
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The migration is underway!

EASTERN MONARCHS
As you may remember, earlier I offered that the recolonization this past May and early June of the summer breeding area was quite favorable. Monarchs generally arrived on time and in good numbers leading to a large second generation. Things looked favorable for a large migratory population that could rival that of 2018 (6.05 hectares) – provided that the summer temps were within 2F of the long-term average and that September temperatures in the north were generally normal as well.

I have been following the weather closely for the last several months and things still look good for a large migration over most of the summer breeding area. However, I have doubts about the number of monarchs that will join the migration from the eastern Dakotas and western Minnesota. Portions of that region have been much warmer and drier than is generally ideal for monarch population development.

In contrast, due perhaps to adequate rainfall and moderate summer temperatures, monarchs are much more abundant in Oklahoma and Texas at this time, suggesting that high numbers of monarchs could join the migration from this region in late September and October. The September temperatures are still a question, but there is no evidence of a drought in Texas or elsewhere that might diminish the possibility of surviving the passage to the overwintering sites.

Overall, while the conditions for population growth have been less favorable than in 2018, suggesting an overwintering population of less than 6 hectares, there is every reason to expect a larger overwintering population in Mexico this year than seen during the last two winters (2.83 hectares for 2019-2020 and 2.10 hectares for 2020-2021).

WESTERN MONARCHS
Given the winter, spring, and summer monarch numbers as well as the extreme summer temperatures and drought conditions in the West, the prospects for an overwintering population of more than a few hundred monarchs along the California coast appear to be slim at best.

For those who would like to delve deeper into the timing, pace and duration of the monarch migration, please see a recent post to the Monarch Watch Blog (https://monarchwatch.org/blog): “Some notes on the sun angle at solar noon (SASN) and the passage of the migration”

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2. Monarch Watch Tagging Kits
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We are in the process of sending out tagging kits for our 30th tagging season – wow! As of today, all preorders and most recent orders going to locations north of (and including) Colorado, Kansas, Missouri, Kentucky, and Virginia have been mailed out. If you are located in that area and you have not yet received your tags, watch your mail for them to arrive within the next 10 days or so. Tags for locations further south will be mailed out soon – priority is always given to those tag orders going to locations that will experience the migration first.

Monarch tagging continues to be an important tool to help us understand the monarch migration and annual cycle – a long-term record is crucial to understand the dynamics of such complex natural phenomena. If you would like to tag monarchs this year, please order your tags soon as they are going fast! Tagging Kits should arrive within 10–12 days but as mentioned above, priority will be given to areas experiencing the migration first.

Monarch Watch Tagging Kits are only shipped to areas east of the Rocky Mountains. Each tagging kit includes a set of specially manufactured monarch butterfly tags (you specify quantity), a data sheet, tagging instructions, and additional monarch / migration information. Tagging Kits for the 2021 season start at only $15 and include your choice of 25, 50, 100, 200, or 500 tags.

Monarch Watch Tagging Kits and other materials (don’t forget a net!) are available via the Monarch Watch Shop online at https://shop.monarchwatch.org – where each purchase helps support Monarch Watch.

2021 datasheets and instructions available online via the Monarch Tagging Program page at https://monarchwatch.org/tagging

Tagging should begin in early to mid-August north of 45N latitude (e.g. Minneapolis), late August at other locations north of 35N (e.g., Oklahoma City, Fort Smith, Memphis, Charlotte) and in September and early October in areas south of 35N latitude. See a map and a table with expected peak migration dates on the Monarch Tagging Program page at the link above.

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3. Submitting Tag Data
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Thousands of you have submitted your recent tag data to us by mail or via our online submission form – thank you! We are still receiving data sheets and if you haven’t submitted your data yet (for 2020 or even previous years) it is not too late. Please review the “Submitting Your Tagging Data” information on the tagging program page then send us your data via the Tagging Data Submission Form. For 2021, please submit your data soon after you are finished tagging for the season.

Complete information is available at https://monarchwatch.org/tagging if you have questions about submitting your data to us and we have conveniently placed a large “Submit Your Tagging Data” button on our homepage at https://monarchwatch.org that will take you directly to the online form.

There you can upload your data sheets as an Excel or other spreadsheet file (PREFERRED; download a template file from https://monarchwatch.org/tagging) or a PDF/image file (scan or photo).

If you have any questions about getting your data to us, please feel free to drop Jim a line anytime via JLOVETT@KU.EDU

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4. Chip in for Monarch Watch
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Our “Chip in for Monarch Watch” fundraising campaign was created in honor of our director and founder, Chip Taylor (whose birthday happens to be at the end of August, by the way). This campaign offers a chance for Monarch Watchers, colleagues, friends, and family across the planet to show their support for Chip and the Monarch Watch program he brought to life more than a quarter-century ago. It has provided tremendous support for Monarch Watch over the years, through both monetary contributions and kind words.

We encourage you to spend a little time reading through previous donor comments on the Chip in for Monarch Watch page (https://monarchwatch.org/chip) – the connections that are facilitated by monarchs and Monarch Watch are truly extraordinary.

The 2021 Chip in for Monarch Watch fundraising campaign is now underway! If you are in a position to offer financial support to Monarch Watch (or know someone who might be), please consider making a donation of any amount during this campaign.

Here’s how it works:
1. Donate online via KU Endowment: https://kuendowment.org/monarch (offline options are also available, see below)

2. Submit your pledge, comments, thanks, birthday wishes, photos, etc. for Chip: https://monarchwatch.org/chip/submit

3. We will assemble a donor list, comments, and photos to present to Chip at the end of the campaign.

Donating securely online is easy but if you would rather make a donation by phone or mail please see complete details at https://monarchwatch.org/chip/

Thank you!

Chip in for Monarch Watch: https://monarchwatch.org/chip

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5. Monarch Waystations
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To offset the loss of milkweeds and nectar sources we need to create, conserve, and protect monarch butterfly habitats. You can help by creating “Monarch Waystations” in home gardens, at schools, businesses, parks, zoos, nature centers, along roadsides, and on other unused plots of land. Creating a Monarch Waystation can be as simple as adding milkweeds and nectar sources to existing gardens or maintaining natural habitats with milkweeds. No effort is too small to have a positive impact.

Have you created a habitat for monarchs and other wildlife? If so, help support our conservation efforts by registering your habitat as an official Monarch Waystation today!

https://monarchwatch.org/waystations

A quick online application will register your site and your habitat will be added to the online registry. You will receive a certificate bearing your name and your habitat’s ID that can be used to look up its record. You may also choose to purchase a metal sign to display in your habitat to encourage others to get involved in monarch conservation.

As of 4 August 2021, there have been 35,768 Monarch Waystation habitats registered with Monarch Watch! Texas holds the #1 spot with 2,922 habitats and Illinois (2,789), Michigan (2,662), California (2,319), Ohio (1,863), Florida (1,788), Virginia (1,602), Wisconsin (1,570), Pennsylvania (1,557) and Ontario (1,179) round out the top ten.

You can view the complete listing and a map of approximate locations via https://monarchwatch.org/waystations/registry

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6. Upcoming Monarch Watch Events
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Monarch Watch Fall Open House
Event Canceled 🙁
Lawrence, Kansas

We had hoped to be able to welcome you back to our Fall Open House event, but we are all going to have to wait a bit longer – sorry! We invite you to visit our garden and enjoy our outdoor space on your own this fall. Evenings and/or weekends would be the best time to visit given the parking restrictions on campus. Thank you for your interest and we hope to see you in person soon. Stay safe!

Monarch Watch Tagging Event (Free event)
Saturday, September 18, 2021
Baker Wetlands Discovery Center
Lawrence, Kansas

The tagging has always been an outdoor event so we are still planning to host it in cooperation with the Jayhawk Audubon Society and the Baker Wetlands Discovery Center – it should be similar to previous years. If you’ll be in the Lawrence, Kansas area in September, we’d love for you to join us so mark your calendars and stay tuned to our website, emails and social media for updates.

Complete details: https://monarchwatch.org/tag-event/

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7. About This Monarch Watch List
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Monarch Watch (https://monarchwatch.org) is a nonprofit education, conservation, and research program affiliated with the Kansas Biological Survey & Center for Ecological Research at the University of Kansas. The program strives to provide the public with information about the biology of monarch butterflies, their spectacular migration, and how to use monarchs to further science education in primary and secondary schools. Monarch Watch engages in research on monarch migration biology and monarch population dynamics to better understand how to conserve the monarch migration and also promotes the protection of monarch habitats throughout North America.

We rely on private contributions to support the program and we need your help! Please consider making a tax-deductible donation. Complete details are available at https://monarchwatch.org/donate or you can simply call 785-832-7374 (KU Endowment Association) for more information about giving to Monarch Watch.

If you have any questions about this email or any of our programs, please feel free to contact us anytime.

Thank you for your continued interest and support!

Jim Lovett
Monarch Watch
https://monarchwatch.org

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Some notes on the sun angle at solar noon (SASN) and the passage of the migration

17 August 2021 | Author: Chip Taylor

Linking the timing, pace and duration of the migration to the sun angle at solar noon (SASN) was only possible because thousands of volunteers tagged monarchs from the time monarchs emerged in late summer until the end of the migration. We now know that the migration begins when the SASN drops below 57 degrees over all latitudes with the monarchs reaching the overwintering latitude in Mexico when the SASN also has dropped below 57 degrees. We also know how the composition of the migration changes from the beginning to the end of the migration and much more.

My intention with this text is to provide you with a better understanding of how the migration is related to SASN and how you can acquire these values for your location and dates of tagging.

The migration lasts 25-33 days in most locations. That means there is a beginning or leading edge (that can either be awesome or a trickle) a peak or midpoint, which usually contains a large portion of the migrants, and an end, which is modest in most years and dominated by smaller monarchs, of which a high proportion are females (relative to earlier in the migration).

The SASN values that correspond to these phases of the migration are as follows.

Leading edge – SASN less than 57 degrees to 54 degrees

Mid-point – SASN from 53-50 degrees

End – SASN 49-46 degrees

For reference, each SASN degree represents a little less than three days. However, that relationship varies slightly with latitude.

It helps to keep in mind that while the above SASN values represent “average rates of movement” of the migration, the migration advances more slowly when it’s too cold, too hot, too rainy or too windy.

To calculate the SASN for a specific latitude and date, go to suncalc.org.

I entered Lawrence, KS, USA. Then clicked on culmination to get the correct SASN value for today. After that I opened the tool box indicated by T and clicked on date slider to open that feature. Once that was open, I closed the tool box. The slider allows you to change the dates easily.

The first image shows the SASN – 64.52 (Altitude in the column at the left) for Lawrence, KS for today 16 August – and the second shows the SASN for the 7th of September – the first day that the SASN drops below 57 degrees (56.81 degrees) for this latitude (N 38°58’23.05”). This date is the earliest date we might expect to see the arrival of migrants from the north in Lawrence. The migrants can be distinguished from non-migratory monarchs, that is those that are still reproductive, since they exhibit directional flight with a distinct heading. In our area, the mean heading for migrants is 210 degrees.

As mentioned, it is only because monarchs have been tagged from the time they emerged in late summer until the end of the migration and beyond that we have been able learn how the migration functions. Given the changing climate which appears likely to affect the migration more and more in coming years, it’s important for taggers to continue the practice of tagging monarchs from emergence of the last generation until the last monarchs pass through each latitude.

Screenshot images from suncalc.org:

Image 1.

Image 2.

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Monarch Population Status

17 August 2021 | Author: Chip Taylor

The migration is underway!

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Monarch Watch Update July 2021

8 July 2021 | Author: Jim Lovett

This newsletter was sent via email to those who subscribe to our email updates. If you would like to receive periodic email updates from Monarch Watch, please take a moment to complete and submit the short Google Form at https://monarchwatch.org/subscribe/

Greetings Monarch Watchers!

Included in this issue:
1. Monarch Population Status
2. Monarch Watch Tagging Kits for 2021
3. Submitting Tag Data
4. Tagging Wild and Reared Monarchs
5. Monarch Waystations
6. Collect Milkweed Seed for Monarch Watch
7. Monarch Calendar Project
8. Upcoming Monarch Watch Events
9. Monarch Rearing, Tagging and Releasing Survey
10. About This Monarch Watch List

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1. Monarch Population Status —by Chip Taylor
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EASTERN MONARCHS
As you may recall, I was concerned about the conditions monarchs would encounter as they returned from Mexico in March due to the devastating impact of the 11-day freeze in Texas in mid-February. That led to a project to determine 1) how the vegetation recovered from the freezing conditions, 2) the plants the monarchs used for nectar and 3) the phenology of the emergence of milkweeds. Those investigations were summarized in two entries posted to the Blog:

Nectar plants used by monarchs during March in Texas
https://monarchwatch.org/blog/2021/05/25/nectar-plants-used-by-monarchs-during-march-in-texas/

Monarchs and the freeze in Texas
https://monarchwatch.org/blog/2021/06/01/monarchs-and-the-freeze-in-texas/

Overall, monarchs seemed to find enough nectar and milkweeds to get the breeding season underway. The next question was where most of the eggs were laid by returning females and would that egg-laying lead to the production of a small, medium or large number of first-generation offspring. Although some of the returning monarch moved north before the appearance of milkweeds, my sense, based on numerous reports from mid to north Texas, was that the majority of eggs were laid in these regions. While the distribution of eggs looked favorable, the larvae still have to reach the adult stage and those first-generation offspring then have to recolonize the breeding areas to the north.

To assess the size of the first generation and success of the recolonization, I rely on the first sightings posted to Journey North. The number of first sightings grows from year to year as more people post their sightings. Nevertheless, I can still get a sense of the year- to-year differences based on the timing of the sightings and their number. To assess what has happened this year from late April to early June, I examined the Journey North first sightings maps from 2010-2021. Tentatively, it looks like the recolonization of the summer breeding range this year is the best ever. I say “tentatively” because I have to look at the data more closely. But it does look like this will be a good year for monarchs.

As of late June, it looks like the recolonization could produce an overwintering population ranging from 2-6 hectares with a real potential to be on the high end of that range. To be at the high end of the range, temperature and rainfall have to be within +/-1.5 degrees and +/-2 inches of the long-term means from now through September. While this prediction holds for most of the range, it is particularly important for the conditions to be close to the long-term average for the Upper Midwest, since it is this region that contributes the greatest number of monarchs to the overwintering population.

For more on the influence of environmental conditions on the development of the populations each year, see this recent blog post:

Monarch population crash in 2013
https://monarchwatch.org/blog/2021/06/11/monarch-population-crash-in-2013/

WESTERN MONARCHS
This spring, Monarch Watch announced a partnership with a California nursery to facilitate distribution of native milkweeds. Californians stepped up and we are currently out of milkweeds for the state but will make an announcement when availability returns. If you are interested in donating native milkweed seed to this cause, please see the “Collect Milkweed Seed for Monarch Watch” item below. Thank you!

Google is taking steps to help address the threat facing California’s monarch butterflies:
Doing our part for California’s monarch butterflies
https://blog.google/outreach-initiatives/sustainability/monarch-butterflies-california/

Review published in Conservation Science and Practice:
Are eastern and western monarch butterflies distinct populations?
A review of evidence for ecological, phenotypic, and genetic differentiation and implications for conservation
Micah G. Freedman, Jacobus C. de Roode, Matthew L. Forister, Marcus R. Kronforst, Amanda A. Pierce, Cheryl B. Schultz, Orley R. Taylor, Elizabeth E. Crone
https://conbio.onlinelibrary.wiley.com/doi/10.1111/csp2.432

From the abstract:
In this review, we focus on phenotypic and genetic differentiation between eastern and western monarchs, with the goal of informing researchers and policy-makers who are interested in monarch conservation. Eastern and western monarchs occupy distinct environments and show some evidence for phenotypic differentiation, particularly for migration-associated traits, though population genetic and genomic studies suggest that they are indistinguishable from one another.

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2. Monarch Watch Tagging Kits for 2021
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Monarch tagging continues to be an important tool to help us understand the monarch migration and annual cycle – a long-term record is crucial to understand the dynamics of such complex natural phenomena. Tags for the 2021 fall tagging season are available and we will start shipping preorders out later this month, ahead of the migration in your area. If you would like to tag monarchs this year, please order your tags soon as they are going fast! Tagging Kits ordered after July 21st should arrive within 7–10 days but priority will be given to preorders and areas that will experience the migration first.

2021 datasheets and instructions will also available online soon via the Monarch Tagging Program page at https://monarchwatch.org/tagging

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3. Submitting Tag Data
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Thousands of you have submitted your 2020 season tag data to us by mail or via our online submission form – thank you! We are still receiving data sheets and if you haven’t submitted your data yet (for 2020 or even previous years) it is not too late. Please review the “Submitting Your Tagging Data” information on the tagging program page then send us your data via the Tagging Data Submission Form.

There you can upload your data sheets as an Excel or other spreadsheet file (PREFERRED; download a template file from https://monarchwatch.org/tagging) or a PDF/image file (scan or photo).

If you have any questions about getting your data to us, please feel free to drop Jim a line anytime via JLOVETT@KU.EDU

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4. Tagging Wild and Reared Monarchs
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As a reminder, the following is an abbreviated version of our “Tagging wild and reared monarchs: Best practices” article posted to our Blog in 2019. The complete text of the article is available via the link below.

Diving into the tagging data has revealed a number of surprises such as the difference between the probability that a reared monarch will reach Mexico and the probability that a wild–tagged monarch will do so. The recovery rate is higher for wild–caught monarchs (0.9% vs 0.5%) and it is the data from the wild–caught butterflies that tell us the most about the migration. Frankly, for some analyses, we have to set the reared monarch data aside. That doesn’t mean it is not valuable, but its uses are limited.

It should be noted that for tagging data purposes, monarchs captured as adult butterflies should be reported as WILD and adult monarchs reared from the egg, larva, or pupa stage should be considered REARED.

TAGGING WILD-CAUGHT MONARCHS
For wild-caught monarchs we need to:
1. increase the number of taggers from western Minnesota and Iowa westward into Nebraska and the Dakotas to give us a more complete understanding of dynamics of the migration;

2. increase the number of wild monarchs that are tagged since these provide the most valuable data; and

3. increase the number of taggers who tag from the beginning of the tagging season in early August until the migration ends. Tagging records for the entire season will help us establish the proportion of the late–season monarchs that reach the overwintering sites. When tagging wild–caught monarchs, many taggers run out of tags well before the season ends. That’s great, but it would help us to know when all tags had been used by indicating this via the online tagging data submission form.

TAGGING REARED MONARCHS
Reared butterflies tend to average smaller than wild migrants. That difference can be reduced significantly if careful attention is given to rearing larvae under the best possible conditions. Large monarchs have the best chance of reaching Mexico, surviving the winter and reproducing in Texas. There are several reasons for this: better glide ratio, better lift with cross or quartering winds, larger fat bodies, more resistance to stress, etc. There are very few small monarchs among those that return in the spring. For those of you who prefer to rear, tag and release, we have a few suggestions:

1. Rear larvae under the most natural conditions possible.

2. Provide an abundance of living or fresh-picked and sanitized foliage to larvae.

3. Provide clean rearing conditions.

4. Plan the rearing so that the newly-emerged monarchs can be tagged early in the migratory season (10 days before to 10 days after the expected date of arrival of the leading edge of the migration in your area).

5. Tag the butterflies once the wings have hardened and release them the day after emergence if possible.

6. When it comes to tagging, tag only the largest and most-fit monarchs (see complete article for some guidelines). Records of tags applied to monarchs that have little chance of reaching Mexico add to the mass of tagging data, but do not help us learn which monarchs reach Mexico – unless the measurements, weight and condition of every monarch tagged and released is recorded. There are a few taggers who keep such detailed records and those data can be very informative. If you collect such data and are willing to share it please contact us; do not add this information to the standard tagging data sheet.

As a final note, this text is not a directive. We are not telling you what to do; rather, we are simply providing suggestions that may lead to more successful rearing and tagging efforts. The expanded version of this article is available at

Tagging wild and reared monarchs: Best practices – https://monarchwatch.org/blog/tagging-best-practices

Have you created a habitat for monarchs and other wildlife? If so, help support our conservation efforts by registering your habitat as an official Monarch Waystation today!

https://monarchwatch.org/waystations

As of 5 July 2021, there have been 34,848 Monarch Waystation habitats registered with Monarch Watch! Texas holds the #1 spot with 2,866 habitats and Illinois (2,695), Michigan (2,572), California (2,255), Ohio (1,803), Florida (1,762), Virginia (1,572), Wisconsin (1,535), Pennsylvania (1,524) and Ontario (1,134) round out the top ten.

You can view the complete listing and a map of approximate locations via https://monarchwatch.org/waystations/registry

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6. Collect Milkweed Seed for Monarch Watch
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Monarch Watch continues to distribute milkweed plugs throughout the monarch range for critical habitat restoration. Please consider donating milkweed seed from wild populations for our partner nurseries to propagate.

Monarch Watch sometimes receives seed donations that perish on the way or in storage. We all want the seed to arrive alive and well-labeled, so please visit the website and read our specific instructions about collecting and donating.

Seed Collecting & Donating Guidelines:
https://monarchwatch.org/bring-back-the-monarchs/milkweed/seed-collecting/

Some areas from which we never seem to have enough of the following seed:

A. tuberosa (butterfly milkweed) from throughout its range, especially Georgia.
A. incarnata (swamp milkweed) from the eastern U.S. states.
A. asperula (antelopehorn milkweed), A. viridis (green antelopehorn milkweed) and A. oenotheroides (zizotes milkweed) from Texas.

Additionally, we need this seed from Arizona and California:

A. angustifolia (arizona milkweed) from Arizona
A. californica (california milkweed) from California
A. eriocarpa (wolly pod milkweed) from California
A. erosa (desert milkweed) from California
A. speciosa (showy milkweed) from California

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7. Monarch Calendar Project
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For those of you participating in our Monarch Calendar project for 2021 (complete details and short registration form at https://monarchwatch.org/calendar/), observation Period 1 has ended (the final date being June 20th, for those of you north of 35N). Once you have logged all of your observations using whatever format works for you (spreadsheet, notebook, calendar, etc.), please use the appropriate online form to submit your data to us:

2021 Period 1 Submission Forms:

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SOUTH (latitude less than 35N)
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Form for Period 1 (15 March – 30 April): https://forms.gle/4imRF4UoVa7TZSnC6

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NORTH (latitude greater than 35N)
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Form for Period 1 (1 April – 20 June): https://forms.gle/KDhVfq5W5duT73vD6

The second observation period runs from 15 July–20 August in the North and 1 August–25 September in the South. As soon as the fall period ends for all locations we will send out links for submission of that data to all who have registered.

Again, complete details and a link to the short registration form are available at https://monarchwatch.org/calendar

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8. Upcoming Monarch Watch Events
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We are tentatively planning to host our annual fall events this year with some changes to the Fall Open House (it will be a shorter outdoor-only event). The tagging has always been an outdoor event so should be similar to previous years. If you’ll be in the Lawrence, Kansas area in September, we’d love for you to join us so mark your calendars and stay tuned to our website, emails and social media for additional details next month.

Monarch Watch Fall Open House (Free event)
EVENT CANCELED
Lawrence, Kansas

Monarch Watch Tagging Event (Free event)
Saturday, September 18, 2021
Baker Wetlands Discovery Center
Lawrence, Kansas

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9. Monarch Rearing, Tagging and Releasing Survey
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In the middle of Covid-19 last June, we conducted a survey of those who rear, tag and release monarchs. Life has been interrupted in many ways over the past year, and we are just now getting around to summarizing the responses (see link below). The number of people who responded (N=1165) exceeded our expectations, and their responses probably represent a good sampling of the reasons people engage in rearing and their rearing practices. Thank you to everyone who participated in our survey!

Monarch rearing, tagging and releasing survey
https://monarchwatch.org/blog/2021/07/06/monarch-rearing-tagging-and-releasing-survey/

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10. About This Monarch Watch List
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Monarch Watch (https://monarchwatch.org) is a nonprofit education, conservation, and research program affiliated with the Kansas Biological Survey & Center for Ecological Research at the University of Kansas. The program strives to provide the public with information about the biology of monarch butterflies, their spectacular migration, and how to use monarchs to further science education in primary and secondary schools. Monarch Watch engages in research on monarch migration biology and monarch population dynamics to better understand how to conserve the monarch migration and also promotes the protection of monarch habitats throughout North America.

If you have any questions about this email or any of our programs, please feel free to contact us anytime.

Thank you for your continued interest and support!

Jim Lovett
Monarch Watch
https://monarchwatch.org

If you would like to receive periodic email updates from Monarch Watch, you may SUBSCRIBE via https://monarchwatch.org/subscribe

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Monarch rearing, tagging and releasing survey

6 July 2021 | Author: Chip Taylor

INTRODUCTION

In the middle of Covid-19 last June, we conducted a survey of those who rear, tag and release monarchs. Life has been interrupted in many ways over the past year, and we are just now getting around to summarizing the responses. While we were targeting those who rear and tag, many people who simply rear and release monarchs responded as well, and we are thankful for those responses. We assured everyone that their information would not be shared and that we wished to simply understand how rearing was being conducted. The number of people who responded (N=1165) exceeded our expectations, and their responses probably represent a good sampling of the reasons people engage in rearing and their rearing practices. As explained below, one of our intentions of the survey was to identify best practices for rearing and releasing. Unfortunately, the survey doesn’t provide the kind of data needed to establish best practices. What it does tell us is that tagged monarchs reared under a broad range of conditions have been recovered in Mexico. It also tells us that while the majority of people who rear, tag and release have not had recoveries, some 20.2% (159/787) reported success. We had hoped that sorting through the conditions reported for those who were successful would help us identify best practices. It doesn’t. There are too many variables which may include things we don’t know about the conditions that lead to diapause and then sensitivity to environmental changes that result in migratory behavior. To sort out the conditions associated with rearing and migratory success, we would have to know the numbers tagged, the dates and locations of release as well as more information about the instars collected or started and rearing methods. We will get those answers in time. In the meantime, we can make some general observations about what needs to be done to rear hardy and healthy monarchs.

Reasons for this survey

As most of you know, Monarch Watch was founded as a monarch tagging program in 1992. At that time, we promoted the tagging of wild caught monarchs, and for a number of years we assumed that our volunteers were only tagging monarchs caught at flowers or collected at overnight roosts. Late in the 1990s, it became clear that some people were tagging monarchs they had reared. At that time, we didn’t pay much attention since rearing and tagging seemed to be a small proportion of all tagging. However, by 2003 it was evident that many more people were beginning to rear, tag and release monarchs. While we didn’t know whether such practices would influence the recovery rate, we decided to be safe, that is, to be able to sort the wild from the reared when analyzing the data. So, we asked participants to indicate on their data sheets, starting in 2004, whether the monarchs they tagged were wild or reared.

Perhaps inspired by the publicity about the decline in monarch numbers and/or the petition to declare the monarch a threatened species, the creation of numerous Facebook sites dedicated to monarchs and other factors, the number of reared, tagged and released monarchs has outnumbered those that are wild caught and tagged for the last several years. Although the tagging records indicate that thousands of reared, tagged and released monarchs arrive at the overwintering sites in Mexico and survive through the winter, it is also clear that the likelihood of reaching Mexico is lower for reared monarchs. We want to know why. We need to sort out why some people who rear, tag and release have much higher recovery rates than others. So, we would like to determine how monarchs have been reared and whether tagged monarchs have been recovered in Mexico.

One reason for the survey has to do with the results in three widely cited studies that proport to show that reared monarchs do not orient properly or are too small or weak to reach Mexico (Davis et al, 2020, Tenger-Trolander, et al 2019, Tenger-Trolander and Kronforst, 2020). While those results may apply to some reared monarchs, it clearly doesn’t explain why almost 2000 reared, tagged and released monarchs have been recovered in Mexico. However, in support of the points raised in these papers, it is clear that the rate of success of reared monarchs in reaching Mexico is much lower than that of wild tagged monarchs. Given that some reared monarchs may lack the ability of orient and migrate, and others may simply be less fit to make the migration, why are many reared monarchs successful in reaching Mexico? It appears that it is easier to fail than to succeed. Although we do not promote rearing and tagging, it seems likely this practice will continue. Assuming this to be the case, we need to understand the reasons for success and failure in order to help those who are engaged in this practice. The survey is the first step in developing a set of standard operating procedures (sops) for rearing that improve the chance that reared monarchs will reach Mexico and will successfully survive the winter. In the end, our objective is NOT to tell people what to do but to provide them with information that will improve the hardiness, health and overall fitness of the butterflies they rear.

Results of the survey

Although 1165 people responded to the survey, because the questions did not apply to all respondents, many of the questions lacked as many answers. Some questions allowed us to assign percentages to the responses. Others did not because two or more of the responses applied or what appeared at the outset to be one question was actually two.

DISCUSSION

As I indicated in the introduction, we expected that we would be able to identify best practices based on the recovery of reared monarchs in Mexico. Specifically, we expected higher recoveries for monarchs reared outside on potted or growing plants that were caged in some way to protect from predators. Next, we expected some success with monarchs reared in cages on porches or other facilities that were exposed to natural temperatures and light. We even expected some success by those who reared monarchs indoors but with an exposure to natural light through windows. What we didn’t expect were reports of recoveries in Mexico by 5 respondents who reared monarchs in rooms without natural light most or all the time. Three of them reared monarchs in rooms with no windows. For monarchs reared in windowless rooms to succeed in entering diapause and then migrating to Mexico is striking. This result is unexpected since it is contrary to studies showing that shortening daylength is required to enter diapause. Further, there were no obvious differences in the number of recoveries of those who reared their monarchs outdoors vs indoors. There were 15 respondents that indicated their rearing was conducted indoors without access to natural light. We need to learn more about these rearing conditions. Since recoveries involve variables, such as point of origin, date of release and numbers released, we will need to dig further into the tagging and recovery data to explain the relationships between rearing conditions and recoveries.

Indoor conditions
Our question dealing with indoor temperatures wasn’t targeted very well and the responses weren’t sufficiently helpful. Observations of the conditions in both the field and lab suggest that diapause induction occurs best when there are distinct differences between day and nighttime temperatures. Night time lows are usually in the 60s, often in the 50s, with mean temperatures of less than 80F. Constant temperatures in the high 70s appear to be too high for diapause induction meaning that the butterflies become reproductive. It follows, that monarchs reared under these conditions would not migrate. More work is surely needed on the factors that lead to both diapause induction and those that lead to reproduction.

Motivation
The motivations of those who rear monarchs were pretty clear. Rearing monarchs is fun, interesting and a bit challenging, and many appear to be motivated to rescue monarch eggs and larvae that would likely be consumed by predators or parasitized by flies. This idea of monarch rescue has resonated and is clearly hard for many to resist. After all, what harm could there be in rescuing a monarch larva from certain death in the mouthparts of a wasp of assassin bug? For many, monarch rescue also means that this practice can contribute to the monarch population, and this goes along with a general interest in monarch conservation. Overall, it’s a powerful combination, something that is fun, combined with the satisfaction of rescuing vulnerable immatures with the notion of adding to the population in a way that contributes to the conservation of the species. Educating children and adults wasalso cited as motivations for rearing. Interestingly, rearing monarchs to tag them was the lowest driver on the list.

Affiliation
Most rearing was conducted at homes (76%) or at a combination of home, school, business and other (11%) with the remaining 13% reared at schools, nature centers and businesses.

Season
Most rearing was conducted in the summer and fall although there were also reports of rearing being conducted in the spring.

Source of eggs and larvae
We were interested in the sources of eggs and larvae used in the rearing since there were some concerns that people were buying stock from commercial breeders that might have been less fit to migrate. However, the responses show that most of the immatures were obtained on their property or nearby properties with only 10 indicating they had purchased eggs.

Female egg layers
We asked a question about obtaining eggs from wild mated females or obtaining eggs from females that were mated to captive bred males. Our curiosity in this case was based on assertions by critics of rearing that inbreeding was involved that would be detrimental to the population. In this case, there were only 18 responses indicating that reared monarchs were allowed to breed and produce eggs. Whether inbreeding occurs under these conditions would depend on the genetic relatedness of the pairings. In the case of brother x sister mating, it could be high, but if the males and females are unrelated, the pairings would be no different from that of wild males and females.

Indoor conditions
Most of the indoor rearing is conducted at room temperature with exposure to natural light through a window. However, there were 15 who indicated that the rearing was conducted in a space with no exposure to natural light. As mentioned above, 5 of these respondents indicated that monarchs reared under these conditions were recovered in Mexico.

Lighting
Most who rear monarchs indoors did not use light timers to increase the photoperiod.

Shelter conditions
This question was really two questions – what type of shelters were used and what were the physical conditions. The only useful information in this case is that most respondents used natural temperatures and light.

Sanitation, washing leaves, fresh food, types of foliage used, crowding and changing practices
These questions were intended to provide some insights about the rearing process. We wanted to know how often rearing containers were cleaned, whether the leaves were washed, how often new foliage was provided, the type of foliage used, how many larvae were being reared together and whether people were changing their practices from time to time to improve their efficiency and success at rearing the larvae to the adult stage. The responses to these questions indicate that most people engaged in rearing have adopted sanitation, feeding and crowding practices that, if followed closely, will lead to the production of healthy monarchs.

Milkweeds
When asked what species of milkweeds were used to feed larvae, there were lots of answers since the use of milkweeds often depends on what is available. Still, there was a clear hierarchy that probably reflects the fact that the majority of those who rear are located in the northeast. Most frequently used was common, followed by swamp, and tropical milkweeds. Of the top 3 used, tropical only accounted for about 11% of the responses.

O. e. questions (Ophryocystis elektroscirrha)
We asked a number of questions about O.e. to determine how those rearing monarchs were dealing with this disease. The sanitation questions fit here as well since washing leaves in particular could eliminate many if not all of the O.e. spores from the leaf surfaces. Still, over 88% of the respondents did not test for O. e. or work with Monarch Health, an O.e. monitoring program directed by Sonia Altizer at the University of Georgia. There were fewer responses to the question about whether monarchs with O. e. were released, but of those, 61% said they did not. We also asked whether monarchs with O. e. were euthanized. This question is similar to asking if monarch with O.e. were released. The answer to the euthanize question generated 635 responses with 72% affirming that they euthanized monarchs with O. e.

Drying time
Because monarchs use most of the first day to mature and are not fully flight capable and therefore vulnerable to predation by wasps, dragon flies and some birds, we asked whether monarchs were released the first day or later. The answers indicated that only about 20% of the respondents routinely allowed monarchs to mature before releasing them. Another 42% indicated that the day of release varied.

Weigh and measure
Since forewing length and overall fitness are related to migratory success, we wondered how many people were aware of this and whether they made the effort to measure forewing length and weigh the monarchs before releasing them. As expected, the majority did not, yet 13 respondents indicated they did weigh monarchs, and 41 said they measured wing length. This question is related to tagging questions regarding whether all or only some reared monarchs are tagged and released.

Tagging
When we asked whether respondents tagged the monarchs they reared, a surprising 32% said no, they only rear to release monarchs locally. Since we were targeting those who rear and tag and didn’t really solicit responses from those who only rear and release, it seems likely that the proportion of those who only rear and release is larger than indicated in this survey. While most of the tagging was conducted during the recommended time framessome 7% indicated they tagged at other times. When we asked if only large monarchs or all monarchs were released, a surprising 14% indicated that they only tagged large monarchs. In the future, we can specify what is meant by large, but since most people were not measuring monarchs or aware of the size issue, we chose not to do so.

Recoveries
There were two questions on recoveries. One asked whether the respondents had recoveries, and the other asked the recovery rate – that is, the percent of all those tagged and released that had been recovered. Surprisingly, 22% reported recoveries and 20 indicated that their recovery rates were 1% or higher. Those are good numbers, typical of those, mostly in the Midwest, who have been tagging wild monarchs for many years.

CONCLUSIONS

The main conclusion we can draw from this survey is that the results, while in some ways robust, are insufficient. These results have failed to indicate that there is a standard or at least a better way to rear monarchs to assure migratory success. In fact, there are no clear trends in the rearing methods and, if anything, they indicate that monarchs reared under a great variety of conditions, including rooms without windows, are capable of entering diapause and successfully migrating to Mexico. An explanation, or at least a partial explanation, of the variability of the success in reaching Mexico may lie in the preconditioning 5th instar larvae experienced outdoors before they were brought into rearing rooms. To determine if this was the case, we compared the recovery rates for those who only reared wild collected 5th instars (N=17) with those who reared small larvae (N=68). The recovery rates were 29% and 19% respectively. Again, not much of a difference from the overall mean of 20.2% with the possibility that the lower % for those rearing small larvae was due to the greater percentage being reared in the East vs the Midwest. Unfortunately, our survey was too general, with many sample sizes that were too small, to pick up on details such as these. Additional information is needed about the rearing conditions, and the age of the larvae, in all cases with recoveries, and we need to know more about the size and mass of those tagged. Further, more experimentation is needed to determine the conditions that lead to the induction of diapause and migratory behavior. We also need to establish the temperatures that block diapause induction or lead to the breakdown of diapause once monarchs begin migrating.

In spite of the limitations of the survey, we can pass along a few observations from the tagging results that bear on migratory success. Analysis of tagged wild and reared monarchs shows that success in reaching Mexico is a function of the site of origin and the date of release. Monarchs released late in the migration and from more distant locations are less successful in reaching Mexico. Further, a number of studies have indicated that large monarchs dominate the leading edge of the migration and apparently have the highest probability of reaching Mexico. Rearing last generation monarchs outdoors on caged rooted or potted plants seems most likely to produce monarchs that enter diapause and migrate. Of course, care should be taken not to expose host plants to egg laying females to prevent O.e. spores from contaminating the leaves. The alternative is to sanitize the rooted or potted plants before using them as food for developing larvae.

REFERENCES

Davis, A. K., Smith, F. M. and A. M. Ballew. 2020. A poor substitute for the real thing: captive-reared monarch butterflies are weaker, paler and have less elongated wings than wild migrants. Biol. Lett.16 20190922.

Tenger-Trolander, A., Lu, W., Noyes, M. and M. R. Kronforst, 2019. Contemporary loss of migration in monarch butterflies. PNAS July 16, 2019 116 (29) 14671-14676

Tenger-Trolander, A. and M. R. Kronforst, 2020. Migration behaviour of commercial monarchs reared outdoors and wild-derived monarchs reared indoors Proc. R. Soc. B.28720201326

TABLES

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Monarch population crash in 2013

11 June 2021 | Author: Chip Taylor

What contributed to the monarch population crash in 2013?

The text below was written at the time the U.S. Fish and Wildlife Service was evaluating evidence of all aspects of the monarch population prior to determining whether the monarch should be listed as a threatened species. As you may remember, in December 2020, monarchs were listed as threatened but precluded based on the priorities given to other species which were more clearly threatened and endangered. A final decision on the status of monarchs is scheduled for 2024. The below was neither published nor posted to this blog. It should have been since the analysis is relevant to what happened between 2016-2018 in California that led to the collapse of the Western monarch population. I’ve reorganized and added to the original text to provide more background and clarity.

INTRODUCTION

There are numerous ways to associate trends in the growth or declines in populations with physical (weather related) and biological factors. Ideally, there are real numbers to work with but that is seldom the case, and lacking hard counts, we often have to link outcomes tentatively with causative factors until we see the patterns appear over and over again in generation to generation or year to year records. That’s the case with monarchs. Numbers are generally lacking with cause-and-effect relationships first appearing as speculation or inference. Those insights, if confirmed again and again, can morph into hypotheses, and in the best cases, correlations, which, in themselves, do not guarantee causation. The next step is prediction. If the outcomes can be predicted based on the observed relationships, we can be reasonably sure we are on the right track.

My approach to trying to understand the trends in monarch numbers has been to use what is called a stage specific model. I break the annual cycle into 6 stages based on the dominant activity within a stage. Each stage is treated as a discrete period that demographically represents either an increase or decrease in numbers depending on conditions during the period but not excluding the condition of the butterflies entering a stage. For example, drought starved monarchs could arrive at the overwintering sites with shorter wings, smaller mass and reduced fat bodies that could affect both mortality during the stage and realized fecundity of the survivors. Further, each stage sets the initial numbers for the next stage, and, in effect, provides limits on what can happen in the next stage irrespective of the conditions during that stage. In other words, the outcome of the next stage depends both on the starting numbers and fitness (mass, fat body, wing area) of the starting population and the conditions during that stage. Good starting numbers may not result in an expected increase if conditions are poor, and conversely, poor starting numbers can effectively cap the outcome even under the most favorable conditions. It also appears to be extremely difficult for a population to recover from a poor start in a breeding season that only involves 3-4 generations.

This approach evolved from attempts to understand the variation in year-to-year measurements of the size of the overwintering monarch population in Mexico. My quest started with a simple question: what was the explanation for the decline from 18.19 hectares in the winter of 1996-1997 to the following winter of 1997-1998 with a population of 5.77 hectares? The answer appears to be an April frost in Texas that killed large numbers monarch eggs and larvae. That quest led to an analysis of the factors possibly associated with population growth for all years from 1994 forward as well as searches through the weather records back to 1895. The point I’m making is that, although this text focusses of what happened from 2011-2015, the data base I’ve used to interpret these records is extensive.

METHODS

The metrics used in this analysis are large scale, or reflect measures of large-scale, that is multi-regional, events. Regional weather and local and regional impacts due to predators, parasites and pesticides all have a role in determining population numbers but are difficult to measure and hard to integrate into a stage specific model. With this in mind, I have selected only a few measures that appear to be correlated with outcomes in a way that give them predictive value. Among these measures are first sightings of adult monarchs in the spring, March temperatures in Texas, May temperatures north of 40N, summer temperatures and NDVI, a measure of greenness of the vegetation on a landscape (Table1). Success or failure of population growth is measured by the increase or decrease in the areas occupied by monarchs at the overwintering sites from one year to the next.

RESULTS

The population declined from 2011 to 2012 and again from 2012 to 2013 and increased in both 2014 and 2015 (Table 1). The declines occurred as the result of high March temperatures in TX (2011, 2012), summer temperatures >1.9F above the long-term means (2011, 2012), drought conditions (low NDVI) in the South Region (2011, 2012) and a low number of first sightings (2013). The increases in 2014 (0.67 to 1.13) and 2015 (1.13 to 4.02) followed favorable mean temperatures for population growth in March, May and June-August. The NDVI index, which can be taken as a proxy for the availability of nectar sources, was high for each year as well

The associations of high mean temperatures and drought conditions with population decreases is seen throughout the record from 1994 through 2019. Similarly, population growth from one year to the next is associated with mean temperatures that are close to or below the long-term average for March in TX. The longer record shows that populations increase when summer means are up to 1.9F above long-term means but decrease when mean temperatures substantially exceed +1.9F. Populations also decline when mean temperatures are >-1.5F below average (2004, 2009).

The temperatures for September and October represent the conditions for the first and second halves of the fall migration (Table 1). Although there is no clear relationship between these means and the size of the overwintering population in these data, this may be changing. The extreme high temperatures for September 2019 delayed the migration by up to two weeks. Those temperatures and a drought in Texas and northern Mexico resulted in an unusually low recovery rate (N=392) for tagged monarchs suggesting that attrition due to these factors limited migratory success. Similarly, above average September temperatures in the Northeast in recent years are associated with lower recovery rates of tagged butterflies from this region.

DISCUSSION

The low number of monarchs reported at the overwintering sites in Mexico in the winter of 2013-2014 appears to have been the result of a series of negative weather events that began in the summer of 2011. Excessive temperatures and droughts in 2011 and 2012 followed by low initial colonizing numbers in the spring of 2013 account for the decline. More favorable conditions for population growth allowed the population to increase in 2014 and 2015.

Temperatures

Summer temperatures can have a significant impact on the size of the fall migratory population. A review of all the records suggests that population growth is enabled when temperatures range from a little over -1F to almost +1.9F. Lower temperatures of >-1.5F, as in the summers of 2004 and 2009, both due to a southward dip in the jet stream, resulted population declines. These reductions may have been due a reduction in egg development which is temperature dependent, egg laying rate or simply a shorter growing season or all three. Average temperatures in the Upper Midwest greater than +1.9F were also associated with declines. Such temperatures are likely to negatively affect realized fecundity by reducing the reproductive activity and longevity of adults. In addition, such temperatures affect resources available to adult monarchs by shortening flowering intervals, and hastening senescence of host plants.

Droughts

A metric known as normalized difference vegetation index (NDVI), a measure of greenness derived from satellite imagery, is frequently used to measure the severity of droughts. Low values indicate severe drought conditions and the NDVI values for Texas were low in both 2011 and 2012. These low values are associated with low recoveries of tagged monarchs and lower than expected overwintering numbers. Drought conditions also occurred in some parts of the Upper Midwest in 2012. Those conditions may have further reduced the migration and the size and robustness of the butterflies originating from that region. Reports of “small” monarchs occur with some frequency during droughts in the Midwest.

First sightings

While first sightings posted to Journey North tend to be urban and suburban centric and can be limited by the number of people willing to report sightings, they appear to tell us two things that are relevant here. First, low numbers, well below the recent average numbers of sightings, as in 2013, tell us that population growth can be limited by the number of returning monarchs. This record also tells us that there is no obvious association between the size of the overwintering population and the number of first sightings. For example, while the overwintering population of 2012 (1.19 hectares) led to 322 first sightings in 2013, the lower population of 2013 (0.67 hectares) accounted for 521 first sightings in 2014. Similarly, the larger population of 2014 (1.13 hectares) produced only 547 first sightings. Sorting out the human factor from the dynamics that produce the numbers of monarchs moving north in March and later in May will be a challenge. In the meantime, the low number returning in 2013 gives rise to several questions about the fitness of the cohort of monarchs that arrived at the overwintering sites in the fall of 2012. We know that most monarchs originate from the Upper Midwest and that the region experienced a semi-drought that summer along with the highest temperatures in the record for that region from 1994 to present. The tagging record for 2012 indicated that numbers tagged that fall were among the lowest we’ve recorded for the Upper Midwest. Therefore, it’s possible that the last generation monarchs were less fit due to lower fat reserves, or size, to survive the migration, the winter period and the migration northward the following spring. High levels of mortality during the migration northward from the colony sites to Texas could also account for the low number of first sightings in the spring of 2013.

Additional considerations

There are a few more things to say about 2012 and 2013 that are not apparent from the above data. The first sightings data show that the return migration for 2012 was the earliest in the record with large numbers of overwintered monarchs advancing beyond 40N in late April and the first 10 days of May. In contrast, due to late arrivals and cool conditions in May of 2013, the movement of first-generation monarchs beyond 40N was predominantly at the end of May. These two back-to-back years demonstrated that overwintering and first-generation monarchs can advance both too early and too late into the summer breeding area for optimal population development. If too early, females lay eggs at more northerly latitudes with cooler, sometimes freezing, temperatures that delay age to first reproduction. Such delays have the effect of reducing the reproductive success of the returning cohort that overwintered in Mexico. Late recolonization also negatively affects population growth in that it shortens the breeding season.

This analysis suggests that it is extremely difficult, maybe impossible, for a population to recover from a poor start in a 6.5-month breeding season that involves 3, and more rarely 4, generations. Of course, this depends on the definition of a poor start, and in this case, I’m thinking of the poor starts in 2004, 2012, 2013. There may have been carry-over effects from the droughts of 2002 and 2012 that had an impact on the populations the following years. The population that developed in 2012, following the drought of 2011 also declined, but that decline may have been due as much to conditions in March and August as to the condition of the butterflies surviving from the previous winter.

This example shows that the decline and recovery of a population can be explained IF measures can be identified that have a broad geographic impact on a population at a particular stage. Negative events can have a ripple effect from one stage to another and can carry over from one year to the next. Further, a series of negative events can cause a population to spiral downward rapidly. Is it possible that the downward trends in the Western monarch population from 2016-2020 were the result of a similar series of negative events? Yes, that’s possible.

The crash in the population numbers in 2013, together with what appeared to be a long-term decline that included other years with alarmingly low numbers (2009-2010 – 1.92 and 2012-2013 – 1.19) led to the petition filed in August 2014 to declare the monarch a threatened species. This petition was preceded by an invitation from the White House to a stake-holders meeting at the Eisenhower Office Building in April 2014. Attendees represented a broad array of organizations interested in monarch and pollinator conservation. A bit later, on the 20th of June 2014, President Obama issued a memorandum requesting that all Federal Agencies with some control of landscapes become engaged with monarch and pollinator conservation. Given the prospect that a small overwintering population would be extremely vulnerable to catastrophic overwintering mortality that could reduce the numbers to levels that would threaten the very existence of the monarch migration, these responses were not unreasonable at the time. The U.S. Geological Survey, the lead research agency of US government, took the lead in convening meetings to examine the monarch situation. These meetings were populated with monarch biologists and appropriate expert personnel from federal agencies. A number of publications resulted from these meetings, the most cited of which is “The all hands-on-deck” paper (Thogmartin, et al, 2017). The analysis therein indicates that an overwintering population of 6 hectares is required for monarchs to be able to rebound from known adverse weather or other events. The analysis also points out that to achieve a population of this size will require the restoration of 1.8 billion milkweed stems. While there are many restoration efforts under way, it’s not clear whether these efforts are sufficient to offset the 2 million or more acres of potential monarch habitat that are converted to croplands and lost to development each year.

The low overwintering numbers of 2013-2014 led me to ask whether monarch numbers had been this low or lower in the past. Yes, that is likely, but there is no data on this subject. What we can do is look at past climates. Those records show that monarchs have experienced far greater extremes in the past than anything seen since 1994. We can only speculate about the impact of these events on monarch numbers, but it seems likely monarchs declined to extremely low levels several times in the last 125 years. And before that was the “little-ice-age”, a much colder period with erratic shifts in climate from 1300 to 1850. While monarchs clearly survived numerous extremes through the centuries, they now face new threats posed by climate change such as severe winter storms, high temperatures and droughts in all portions of the breeding season and even the migration. Those impacts can already be seen in California.

Table 1. Temperature means, first sightings and NDVI records for 2011-2015.

	2011	2012	2013	2014	2015
Overwinter hectares/prev season	4.02	2.89	1.19	0.67	1.13
First sightings 1 March–30 April	241	255	129	201	203
March mean temp TX	+5.4	+6.8	+0.9	-1.6	-0.2
May mean temp 40N UM	-0.2	+4.8	+0.2	+0.5	+1.3
First sightings >40 N 1 May–9 Jun	362	408	193	320	344
June–August mean temp Upper Midwest	+2	+3	+0.3	-0.5	-0.3
September mean temp Upper Midwest	-0.5	-0.1	+3.3	+0.5	+6.4
October mean temp South Region	0	-1.3	+0.1	+2.9	+2.6
Total first sightings	603	663	322	521	547
NDVI	0.462	0.494	0.536	0.542	0.533

REFERENCES

Wayne E Thogmartin, Laura López-Hoffman, Jason Rohweder, Jay Diffendorfer, Ryan Drum, Darius Semmens, Scott Black, Iris Caldwell, Donita Cotter, Pauline Drobney, Laura L Jackson, Michael Gale, Doug Helmers, Steve Hilburger, Elizabeth Howard, Karen Oberhauser, John Pleasants, Brice Semmens, Orley Taylor, Patrick Ward, Jake F Weltzin and Ruscena Wiederholt. (2017). Restoring monarch butterfly habitat in the Midwestern US: ‘all hands on deck’. Environmental Research Letters, Volume 12, Number 7 074005 https://iopscience.iop.org/article/10.1088/1748-9326/aa7637

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Monarchs and the freeze in Texas

1 June 2021 | Author: Chip Taylor

by Chip Taylor, Director, Monarch Watch; Carol Clark, Monarch Watch Conservation Specialist; and Janis Lentz, Volunteer

The following is a long report about the impact of the freeze in February 2021 on the development of this year’s monarch population. If you are into monarch biology and monitoring, this report is worth a read. In addition to observations on monarch biology, we compare iNaturalist and Journey North records over several years. There are interesting similarities and differences in these records and from year to year.

INTRODUCTION

As most of you know, I make an effort to follow the monarch population as closely as possible every month of the year. Thus, it was with some alarm that I read about the period of freezing weather in Texas in mid-February. I was alarmed because it was clear that the freeze killed most of the vegetation then in leaf over a broad area of Texas and northern Mexico. This realization gave rise to the possibility that monarchs returning from Mexico in mid-March would find little or no milkweed to lay eggs on or flowers in bloom with nectar to sustain them. These concerns led me to post several notes to Dplex-L, our email discussion list, proposing to monitor the recovery of the vegetation coincident with the arrival and behavior of monarchs throughout the month of March. I was obviously fumbling for a way to conduct such a survey when John Barr posted the suggestion that iNaturalist (iNat) might be able to provide the platform and the number of observers throughout Texas needed to monitor the development of milkweeds and determine the nectar sources used by monarchs. I was unfamiliar with iNat, but could see the potential this photo-based reporting system had for providing the information I was seeking. Subsequently, with the help of John Barr, Carol Clark and several others, we created a list of potential floral sources returning monarchs might visit for nectar. We also created a text which outlined our objectives and launched the project with the assistance of Tania Homayoun, of the Texas Parks and Wildlife Department, on the 2nd of March.

The following narrative starts with an abbreviated version of the project outline posted to iNat and then moves on to a summary of the results and shows how these records compare with those of previous years. The text ends with a discussion of the strengths and limitations of this means of monitoring the monarch population along with a number of suggestions as to how the data generated from this project could be mined to gain further information on floral usage by monarchs and how weather factors influence monarch behavior.

Texas Winter Storm 2021 Plant & Pollinator Survey

“The February freeze damaged vegetation across Texas. We’d like your help tracking the recovery of plants that flower in March along with milkweeds. Both are resources used by monarchs returning from Mexico in mid-March and their availability will determine how well the monarch population develops in 2021.

The 11-day cold spell (10-20 February) in Texas was a disaster (see Maeckle, 2021, Severson, 2021 and Texas Parks and Wildlife, 2021). Freezing temperatures covered the state and extended well into northern Mexico. While many of the immediate effects of the freeze are clear, season-long and multiple-year effects may linger. The damage to the flora was extraordinary, and it is likely that nearly all above-ground insects died over a wide area. Plants already in flower may have been so damaged as to not flower this year. We are seeking help to record that damage and the recovery of plants that flower in March along with the appearance of milkweed shoots and buds. Both are resources used by monarchs returning from Mexico in mid-March. We also need help recording the number of returning monarchs. ALL monarch observations are of value. How well the monarch population will develop in 2021 will be determined by the March conditions in Texas.

Since we know the freeze ended on the 21st of February, that becomes day 1 when assessing plant development. We can determine the number of days after the freeze that it took for a species to recover. Those dates can be compared to the long-term peak flowering for a species to determine if flowering was delayed. Monarchs generally reach the milkweed-rich areas of Texas around 12-15 March and the question that follows is: Will arriving monarchs encounter milkweeds and nectar plants in sufficient abundance, or will they encounter a landscape still too deep in recovery to provide the needed resources to establish the next monarch generation?”

Simply stated, the main goal of the project was to determine how well the arrival of monarchs returning from Mexico matched up with the regrowth of milkweeds and the appearance of nectar sources. The initial assumption was that a lack of both nectar and milkweeds would result in shorter life-spans for the monarchs and reduced egg laying, resulting in a negative impact on the growth of the population in 2021.

METHODS

The methods involved tracking the postings to iNat of monarchs and emerging milkweeds through March. The numbers of monarch reports were compared to those reported to Journey North (JN) on the same days.

The results consist of photographic records posted to iNat of monarchs and the three common milkweed hosts for monarch larvae – antelope-horn (Asclepias asperula), green antelope-horn (A. viridis) and zizotes (A. oenotheroides) milkweeds. The distributions of the monarch and milkweed locations reported for March 2021 are shown in Figures 1-4.

Since 12% of the monarch images were of butterflies feeding on the nectar of various flower species in 2021, it was possible for CC to create a list of plants monarchs used as nectar sources throughout the month. CC also scanned iNat images for nectaring by monarchs in March 2020 (13% of images) and March 2018 (45% of images). A list of these plants visited in 2021 is shown in Table 1. A separate article for the Blog includes the plants monarchs were observed feeding on in March 2020 and 2018.

To provide a larger context for the observations of monarchs recorded in 2021, the numbers of monarchs reported to iNat for 2020 were also tallied, and the numbers of adult monarchs for each year were then compared with the number of first sightings reported to JN for both years.

RESULTS

The complete record of all images posted for March can be found on the iNat project page at inaturalist.org/projects/texas-winter-storm-2021-plant-pollinator-survey?tab=species.

Comparison of iNaturalist and Journey North first sightings
The first set of summaries includes all monarchs recorded for iNat and JN for 2021 as well as the first sightings reported for Texas to JN for 2020 (Figs. 5-7). First, the number of records for iNat in 2021 exceeded those reported to JN by a significant margin (534 vs 311). The 311 for JN for Texas in March actually exceeded the previous high number which was the 226 recorded in 2020. A second feature for the 2021 data is the parallel numbers, with JN being slightly ahead from 1-17 March. Thereafter, the reports to iNat continue at a high level while those of JN are relatively lower. This result may indicate that the number of people willing to report to JN has become saturated as discussed below. If so, then the numbers of monarchs on the move, mostly in North Texas, in late March are underrepresented. A third thing to notice is the human-centric distribution of the reports with the biggest numbers associated with the major human concentrations, first in the vicinity of San Antonio and Austin and then Houston followed by the greater Dallas area. You can also see the effect of a cool, cloudy day (22 March) in both records.

Taking all three records together, it’s apparent that there was an abrupt increase in observations on the 10th of March. A comparison of the number of sightings before the 10th in 2020 vs 2021 may say something about the impact of the freeze on monarchs already in Texas before the arrival of monarchs from Mexico. In 2020, a year without a freeze, 34 sightings were reported before the 10th (15% of 226) while in 2021 there were 19 in the JN record (6% of 311) and 18 in the iNat data (3% of 534). While the 2021 iNat images did indicate that some monarchs, judging by their fresh appearance, had survived the freeze, the number was low.

The iNat monarch numbers for 2021 and 2020 are summarized in three histograms for each year (Figs. 8-13). On the assumption that all images, whether they represented eggs, larvae, pupae or adults represented a monarch at one time or another, the first histogram includes all records. To make comparisons with the first sightings reported to JN, a second set of histograms included only adult monarchs. The third set showed the distribution through March of the reports of immatures.

Recolonization of Texas by monarchs migrating north from Mexico

The numbers of records posted to iNat and JN for both 2020 and 2021 (Figs. 5-7) show a strong increase in reports starting on the 10th of March each year. This increase in reports continued in both iNat and JN in 2021 until the 18th and then declined as monarchs advanced beyond San Antonio and Austin only to increase again after the 22nd when monarchs reached the more densely populated areas in North Texas.

Monarchs enter Texas through via two routes, one a pathway into the Edwards Plateau west of San Antonio through Del Rio, Texas, and Uvalde, and the other along the coast from Brownsville to Houston. The latter route is represented by numerous images posted to iNat and a number of JN sightings. The western route is less well represented by reports to either program. The low number is likely due to the lower human density along that pathway. The number of reports in the Rio Grande Valley, the region between the two pathways, is usually low in both the spring and the fall due to the higher temperatures in that region. Monarchs appear to prefer routes with lower temperatures.

Milkweeds
The geographic distributions of the three milkweed species based on the submitted photos are shown in Figures 2-4. The distributions of these reports through the month are shown in Figures 14-16. These figures, though based on limited data, demonstrate that zizotes (N=60), the species with the most southerly concentration, was the first to appear after the frost. The occurrence of antelope-horn milkweeds (N=203) followed with a distribution that was generally in the Edwards Plateau west of San Antonio and Austin. Last to appear was the green antelope-horn (N=34). This milkweed is the most abundant and widespread of the three major milkweed hosts used by monarchs in Texas. The low number of sightings for this species apparently lies with the distribution of people willing to report milkweeds to iNat. Green antelope-horn is the dominant milkweed in the vast area east of I-35, an area of ranches, some cropland and relatively few people. This result again demonstrates how dependent monitoring of this type is on the distribution of people.

Immatures
Perhaps the starkest contrast between the iNat numbers for 2020 and 2021 was the number of images of immatures (eggs, larvae and pupae) in the 2020 data (N=186, 29% of all observations) and 2021 (N=25, 5% of all observations). Further, immatures were reported throughout the month of March in 2020 (Fig. 13) but only in the second half of March in 2021 (Fig. 10). Since, the dates of arrival of monarchs in Texas were similar for both years, the contrast between the two years in the distribution of immatures may have been due to a breeding population of monarchs (offspring of overwintered monarchs) in 2020 as well as the delay in the emergence of milkweeds due to the freeze in 2021.

Nectar sources
Visual scans of the iNat images by CC for examples of monarchs nectaring at flowers produced a list of 69 species in 2021, 85 in 2020 and 41 in 2018 for a total of 123 species. Of these, only 20 were visited in all three years, while 30 of those used in 2021 were not visited in either of the other two years. Further, species used in the other two years, were either not present in 2021 or were not seen to be used by monarchs. A list of the 2021 plants is shown in Table 1.

DISCUSSION

This project was based on the concern that milkweeds and nectar sources would not be available to monarchs returning from Mexico in mid-March due to the devastating impact of the 10-20 Feb freeze experienced over much of Texas. These concerns center on three main questions: 1) would monarchs get ahead of emerging milkweeds, 2) would nectar sources be lacking and 3) would the development of the first generation be hindered due to the impact of the freeze?

While it seemed clear that some monarchs advanced northward faster than milkweeds emerged, with a number even moving into Oklahoma much too early, the numbers that advanced relative to the total number of monarchs moving into Texas was not clear. Temperatures were moderate through most of the month which may have allowed many female monarchs to survive to lay eggs once the milkweeds emerged. Subsequent reports of an abundance of eggs and larvae on milkweeds from Central to North Texas, and a delay in the advance of more monarchs into Oklahoma, suggested that most of the eggs laid by returning monarchs were laid in Texas – an outcome that is more favorable than egg laying in more northerly locations where the temperatures are lower and developmental time for immatures is longer. So, the answer to this question seems to be yes, some monarchs did get ahead of the emergence of milkweeds, yet, in spite of the late appearance of milkweeds, most eggs were laid in Texas.

As to the abundance and diversity of nectar sources, monarchs were photographed utilizing flowers of 69 different species. While this number was fewer than in 2020 (N=85), and involved sources seldom used in good years, monarchs appeared to adapt to the new conditions. While we can’t say anything about the distribution and abundance of the nectar sources across Texas in 2021, many of the nectar sources involved species that are widespread and moderately abundant. Of particular interest was the fact that of the 123 species visited by monarchs in our survey of iNat images over a three-year period only 45% (N=55) were native to Texas. This result is a testament to monarch’s adaptability but also says something about the human/urban-suburban distribution of the observers and introduced plants. A more complete analysis of the nectar plant results can be found at monarchwatch.org/blog/2021/05/25/nectar-plants-used-by-monarchs-during-march-in-texas/.

That brings us to the last and most important question. Was the development of the first generation hindered by the conditions created by the freeze? At this writing (late-May), that doesn’t appear to be the case. The number of first sightings reported to JN through 25 May is equal to or greater than the numbers reported for several years with good overwintering numbers. However, to be clear, to make predictions, we need data on the size of the first generation in the form of reports to JN and iNat of monarchs colonizing the latitudes north of 40 N from mid-May to 10 June. If the weather is favorable for recolonization and the numbers are low, that will be an indication that the first generation was affected by the spring conditions in Texas. High numbers recorded through the 10th of June would indicate that the storm had little effect on the development of the first generation. Overall, given the reports of large numbers of eggs and larvae from several Texas locations in April, there is still a reasonable possibility that the overwintering population will increase this year.

There is one more consideration of interest. Will the freeze have an impact on the incidence of O. e. in the 2021 monarch population? As noted earlier, there was a near total lack of “fresh” monarchs seen in the iNat records before 10 March for 2021. These records are in contrast with the record for 2020, 19 vs 34 (Figs. 10,13). Further, there were no eggs and larvae until mid-March in 2021 vs eggs and larvae throughout the month in 2020. The fresh monarchs in 2020 were presumed to be offspring from late winter reproduction that matured on tropical and, more rarely, native milkweeds. Since the freeze in 2021 apparently froze all above ground vegetation including milkweeds and most resident monarchs, these sources of O. e. spores would have been lacking as monarchs returning from Mexico moved into Texas in 2021. In theory, a lower contact with spore-infested plants and spore-carrying adult monarchs could result in a lower incidence of O. e. in the monarch population as the season develops. The assumption made by some observers has been that, in normal years, such as 2020, there is enough contact between spore-infested plants and spore-carrying resident monarchs to increase the incidence of O. e. through the season. The question that follows is: Will the rate of O. e. infected monarchs be lower, the same or higher at the end of the 2021 season?

Strengths and limitations of iNaturalist and Journey North monitoring of monarch numbers

We need monitoring of monarch immatures and adults throughout the year to help us understand monarch population dynamics. Dynamics means we are asking how the monarch numbers are influenced by biological factors such as predators, parasitoids, O. e. and xenobiotics (man-made chemicals) as well as by the variation in the weather throughout each year and from year-to-year. At the same time, we need to define and fully understand the strengths and weaknesses of each monitoring method. With respect to iNat, we need to acknowledge that the process of obtaining the images has inherent biases. First, the very process of taking pictures involves light with most pictures taken when the photographer determines there is enough light for a photo. Then, there are the hours that both monarchs and people overlap in the field. While both monarch and human activity probably have similar peaks in early to mid-afternoon it’s possible that there is less overlap both early and late in the day that could result in missed opportunities to record monarch activities. It may also be the case that monarchs are more active than the iNat participants when the temperatures are in the 60F. Further, it’s clear that the records are human-centric in that they are concentrated around major cities. This means that large areas in the countryside, which are usually slightly cooler and dominated by native rather than introduced vegetation, are seldom visited. There is also a matter of numbers and picture taking in that many monarchs may be seen, but only the ones that sit still long enough to be photographed get to be part of the record.

A strength of the iNat records is that we have time-coded photos, many of which provide information on monarch behavior, nectar feeding and condition of the wings. Further, the iNat observers can post numerous images/records of monarchs through an observation period. The JN first sightings data are also of great value in that they indicate the timing of colonization by monarchs returning from Mexico and later in the spring the migration of their offspring across the latitudes and longitudes to the north and northeast. These data have helped us understand how the population develops each year. However, they have one limitation – they are first sightings only and don’t capture abundance. To fully understand population growth of the monarch population, we need data on both the timing and abundance of monarchs moving in to new areas. As it stands, we have to infer abundance from the number of first sightings posted for a region. That fails when there are too few participants in a region. In effect, this means that the population of observers willing to post to JN becomes saturated. Given this limitation, to assess abundance, we need to use both iNat and JN data, perhaps in combination with other data sets. A close look at the images posted to iNat shows that there are small numbers of duplicate records (2.8% in 2021, Fig. 8). JN vets their sighting data, but there are a few errors in their data set as well. Rather than questioning all records, we ignored them due to their small number.

Future projects

The iNat data could be mined to determine how weather patterns from year-to-year affect flowering plants and monarchs. For example, it would be easy to compare the phenology of the top 10-20 flower species monarchs use and then to compare that with how frequently those flowers are visited by monarchs. This type of phenology matching is being attempted with a number of pollinators. In addition, one could examine how the use of some species is affected by the simultaneous flowering of other species. Since there is a time code associated with each photograph, it should be possible to dig a bit deeper into nectar usage. It is known that some plants only produce nectar once the daytime temperature reaches certain point. That is known to influence honey bee foraging and may well affect butterfly foraging as well. In other words, nectar feeding by monarchs could be determined not just by floral abundance but by the ambient temperature and therefore the time of day. The time codes also offer an opportunity to bracket the range of temperatures at which monarchs operate. The goal would be to not only show the range of temperature, solar and wind conditions that are recorded for a specific activity such as egg laying, mating or migrating, but to identify the optimal conditions for these activities. To make those connections between behavior and weather, we can draw on the proliferation of Tempest weather stations. I will describe how this can be accomplished in another Blog article.

To see the data provided by these weather stations, please visit our Tempest weather station at Monarch Watch via www.wunderground.com/dashboard/pws/KKSLAWRE185

Earlier, we pointed out that because the freeze ended on the 21st of February, that date could be used as a start point to determine the extent to which flowering had been delayed or eliminated in 2021 relative to the flowering of these same species in more typical seasons. We will leave that project to others.

REFERENCES

Maeckle, M., 2 March, 2021. Wildlife death toll mounts in wake of historic Texas freeze. San Antonio Report. sanantonioreport.org/wildlife-death-toll-mounts-in-wake-of-historic-texas-freeze/.

Severson, K., 5 March 2021. Texas Farmers Tally Up the Damage From a Winter Storm ‘Massacre’. N. Y. Times. www.nytimes.com/2021/03/04/dining/texas-farms-storm-damage.html.

Texas Parks and Wildlife, March 10, 2021. At least 3.8 Million Fish Killed by Winter Weather on Texas Coast. tpwd.texas.gov/newsmedia/releases/?req=20210310.

FIGURES AND TABLE

Figure 1. Monarch distribution as of 6 April 2021 (N=534).

Figure 2. Antelopehorn milkweed (Asclepias Asperula) distribution as of 6 April 2021 (N=203).

Figure 3. Green antelopehorn milkweed (Asclepias viridis) distribution as of 6 April 2021 (N=34).

Figure 4. Zizotes milkweed (Asclepias oenotheroides) distribution as of 6 April 2021 (N=60).

Figure 5.

Figure 6.

Figure 7.

Figure 8. *Duplicate & questionable records removed.

Figure 9.

Figure 10.

Figure 11.

Figure 12.

Figure 13.

View larger image of Figures 8-13 as a group.

Figure 14. Images of zizotes milkweeds (Asclepias oenotheroides) submitted to iNaturalist in March 2021.

Figure 15. Images of antelopehorn milkweed (Asclepias asperula) submitted to iNaturalist in March 2021.

Figure 16. Images of green antelopehorn milkweed (Asclepias viridis) submitted to iNaturalist in March 2021.

Table 1. Nectar sources visited by monarchs in March 2021.

COMMON NAME	SCIENTIFIC NAME
Mexican Plum	Prunus Mexicana
Crow Poison/False Garlic	Nothoscordum bivalve
Dakota Mock Vervain	Glandularia bipinnfidia (and related species)
Cherry Laurel	Prunus caroliniana
Citrus sp	Citrus spp.
Thicket Plums/Wild Plum (collective)	Prunus spp
Redbud,	Cercis canadensis, multiple subspecies
Dandelion	Taraxicum officinale
Henbit	Lamium amplexicaule
Lilac	Syringa vulgaris
Bull Thistle/Bristle Thistle/Yellow Thistle	Cirsium horridulum
Crimson Clover	Trifolium incarnatum
Tropical Milkweed	Asclepias curassavica
Heller's Marbleseed	Onosmodium helleri
Amur Honeysuckle	Lonicera mackii
Dewberry/Blackberry	Rubus spp
Bastard Cabbage/Wild Mustard	Rapistrum rugosum
Texas Ragwort	Senecio ampullaceus
Yaupon Holly	Ilex vomitoria
Pear	Pyrus spp., callereyana, and fruiting pears
Anacua	Ehretia anacua
Mexican Buckeye	Ungnadia speciosa
Verbena	Verbena spp
Indian Paintbrush	Castilleja spp, only Castilleja indivisa shown
White Dutch Clover	Trifolium repens
Mesquite	Prosopsis glandulosa
Willow	Salix spp, likely Salix nigra
Phlox	Phlox spp
Apple	Malus
Soft Marbleseed	Onosmodium bejariense
Peach	Prunus persica
Duranta	Duranta erecta
Astragalus	Astragalus spp.
Fleabane	Erigeron spp, likely E. philadelphus, others?
Marigold	Tagetes?
Mealy Blue Sage	Salvia farinacea
Texas Toadflax	Nuttallanthus texanus
Pink Evening Primrose	Oenothera speciosa
Possumhaw Holly	Ilex decidua
Buttercups	Ranunculus spp
Roughleafed Dogwood	Cornus drummondii/Swida
Agarita	Berberis trifoliolata
Texas Madrone	Arbutus xalapensis
Bigtooth Maple	Acer grandidentatum
Texas Thistle	Cirsium texanum
Petunia	Petunia sp.
Crocus	Crocus sp
Brazoria	Brazoria sp
Goldenball Leadtree	Leucaea retusa
BlackJack Oak	Quercus marilandica
Oxalis	Oxalis spp.
Aromatic Sumac	Rhus trilobata, Rhus aromatica
Red Buckeye	Aesculus pavia
Hackberry	Celtis sp.
Cutleaf /Sawtooth /Engelmann's Daisy	Engelmannia peristenia
Imported Holly	Ilex spp
Death Camus	Zigadenus nuttallii
Eastern BlueStars	Amsonia tabernaemontana
Texas Bluestars	Amsonia ciliata
Rabbit Tobacco	Diapera sp
Cedar Elm	Ulmus crassifolia
Pansy	Viola × wittrockiana
Texas Ebony	Ebenopsis ebano
Gerbera Daisy	Gerbera jamesonii
Bur Clovers	Medicago spp
Live Oak?	Quercus virginiana
Buttonweed	Diodia virginiana
Rangoon Creeper	Quisqualis indica
Vetch	Vicia spp

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