14 October 2015 | Author: Monarch Watch
Submitted by Candy Sarikonda, Monarch Watch Conservation Specialist
South Bass Island monarch roost at dawn in hackberry trees 2015. Photo by Candy Sarikonda.
Recently, I visited South Bass Island in Lake Erie for a weekend of monarch activities. The Lake Erie Islands are favorite stomping grounds of mine for many reasons, but chief among them is the opportunity to witness the annual fall monarch migration moving through the islands. For over four years, colleagues and I have been working to document monarch activity in the Lake Erie islands region. Through our documentation and the reports of other citizen scientists, we have found evidence that monarchs do cross Lake Erie, and they do so deliberately and successfully.
While scientists are aware that monarchs can cross water, it is not well understood how monarchs cross the lake and under what conditions they will do so. Specific observations are few. Physical conditions such as wind direction, wind speed and temperature during these transits are not well understood. Reports from citizen scientists can serve to increase our understanding of the monarch migration over bodies of water. This article will share the stories of citizen scientists throughout the Great Lakes region, highlighting reports primarily from observers in Lake Erie and Lake Ontario, but also a few reports from Lake Michigan.
Why do monarchs cross the Great Lakes?
There is some explanation for this, particularly as it relates to Lake Erie. Dr. Chip Taylor has provided an explanation of monarch movements through southern Ontario, along the north shore of Lake Erie. Dr. Taylor explains, “During the fall migration in southern Ontario, Monarchs cluster together on trees to form overnight roosts in a manner similar to the dense aggregations formed at the overwintering sites. Overnight roosts may contain a few hundred to several thousand individuals, and monarchs usually form clusters in the same areas year after year. The location of overnight roosts is largely determined by topography, and proximity to abandoned farmlands with abundant nectar resources such as fall composites (asters and goldenrods). Monarchs migrating south in the fall through southern Ontario build up in numbers along the north shores of Lake Ontario and Lake Erie. Their apparent reluctance to fly over large bodies of water, coupled with the desire to continue moving southwards, probably causes the butterflies to fly southwestward following the shoreline. This inevitably results in large concentrations of monarchs accumulating on peninsulas jutting out into the lakes, where they have little choice but to eventually proceed southward over open water. Large aggregations and overnight roosts occur at many locations on peninsulas and at other locations along the lakeshores, including Presqu’ile Provincial Park, Long Point, Rondeau Provincial Park and Point Pelee National Park.” (www.monarchwatch.org/read/articles/canmon2.htm)
One of the main stopover sites for monarchs migrating along the northern Lake Erie shoreline is Point Pelee, located in Leamington, Ontario, Canada. Each fall, naturalists and observers at Point Pelee National Park report hundreds or thousands of monarchs gathering at the tip of the peninsula, awaiting favorable weather and a good tailwind that will enable them to cross the lake safely. Most often, monarchs gather at the tip ahead of a storm or cold front, or during times when winds from the south create a significant headwind. Monarchs will remain at the tip and nectar as they wait for favorable air temperatures and calmer, more northerly winds. Once the weather is suitable, they will continue their migration across the lake.
Observers have reported the behavior of monarchs as they fly out over the lake. Citizen scientist Darlene Burgess frequently observes monarchs roosting at Point Pelee National Park. Burgess has reported roosts of 4000-5000 monarchs at the tip of the peninsula. She has noticed that northerly winds tend to facilitate the migration, whereas strong southerly winds and storm fronts will cause monarchs to gather at the tip. Burgess shared this observation, “On Saturday, September 19, 2015, a strong storm moved into the area. Winds were from the southwest at 16-18mph with gusts of 23-35mph. Over 5,000 monarchs roosted at the tip. The next morning, winds were from the north at 9 mph. As the sun rose, monarchs roosting on the east side of the trees began basking, and quickly began to disperse. Most were dispersed by 7:45 am. The three largest roosts broke up by 8:30am. The monarchs flew to the shoreline trees, and then began flying out over the water in groups of 6-8 individuals, initially about 60 feet over the water. They appeared to be testing the wind and their strength. Some would fly back to the trees, but the majority continued on. As they continued south over the lake, they flew even higher, up to 100 feet. I was able to watch them for some distance with my star-gazing binoculars. They continued on, flying due south, at a height of about 60-100 feet above water. This continued on until about 12:30pm, when all monarchs were gone from the tip.” She further reports, “I observed on another day with a strong southeasterly wind that the monarchs were leaving low from the shoreline. They were again flying out in groups of 6-8, testing the winds. Most returned to shoreline trees, with only a few continuing on each time. That’s the day I painfully watched two monarchs fly south about a foot over the 1-foot waves…I was so concerned the waves would hit them. I did observe them attempt a higher altitude of 10-15 feet, but not for more than a second or two before returning to their low flight and flying out of view.”
Beall, in 1941, reported his observations of monarchs leaving the shoreline. He noted that “monarchs starting out over the lakes from the shore, flew either with or against the wind.” He felt there was no marked tendency for monarchs to move either with or into the wind, and thus concluded that monarchs were not simply being pushed around and dispersed passively but were instead flying with deliberate purpose. He enlisted the aid of the Southey Shoals lighthouse keeper to document monarch movements over Lake Erie from 1937-1938. The lighthouse is located 7 miles off Point Pelee. The keeper recorded flight direction for monarchs passing by the lighthouse, and data showed a preponderance of monarch flight to the south, with some lesser movement to the southeast (Beall, 1941).
Can monarchs cross Lake Erie successfully?
Directly south of Point Pelee are the Lake Erie Islands, located in the western basin of Lake Erie. My colleagues–naturalists Jackie Taylor of the Lake Erie Islands Nature and Wildlife Center (LEINWC), and Nicole King of the Ohio State University’s Stone Laboratory–and I have been actively documenting the monarchs that migrate through the Lake Erie islands since 2011. I have assisted with tagging efforts and worked to locate and photograph fall roosts. Taylor and King have tagged dozens of monarchs at the South Bass Island lighthouse grounds, while also monitoring monarch migratory and reproductive behavior on South Bass Island and the surrounding islands. Taylor and King have documented monarchs reproducing on South Bass Island and Gibraltar Island, and Taylor has observed monarchs reproducing and migrating through Pelee Island, North Bass Island and Middle Bass Island. Taylor, along with Katie Hollenbeck of Stone Laboratory, carried out a tagging effort during September 24-25, 2012. During that 2-day period, winds were 8mph from the southwest, and Taylor and Hollenbeck tagged a total of 236 monarchs that resulted in three recoveries of tagged monarchs at El Rosario. These recoveries provide evidence that monarchs can cross Lake Erie from South Bass Island to the OH shoreline, a distance of three miles, and continue to migrate to Mexico successfully. In addition, I documented 400 monarchs roosting on South Bass Island on September 13, 2014 and again documented a roost of 400 monarchs that formed on the island the evening of September 12, 2015. Clearly, these monarchs were not produced on South Bass Island, strongly suggesting a more northerly, off-island origin. Miller Ferry services the Lake Erie islands, and captains and deckhands report annual observations of monarchs flying over the water toward the OH shoreline, usually at 20-30 feet above the water. Captain Glenn Cooper states, “I usually see 2 or 3 a day during the fall. They fly at the level of the pilot house,” a height of about 25 feet off the water.
Jackie Taylor of LEINWC and Kesari Sarikonda 2012. Photo by Candy Sarikonda.
In addition to evidence reported in the Lake Erie islands, there are reports along the OH shoreline further east of the islands and on the water as well. Jen Brumfield, a naturalist with Cleveland Metroparks, reported a large roost of 4000 monarchs gathered at Wendy Park on Whiskey Island on the evening of September 12, 2015. Wendy Park is located directly on the southern shore of Lake Erie near downtown Cleveland, and has long been known by area residents as an annual stopover site for migrating monarchs. Brumfield reported “…After crossing Lake Erie, thousands upon thousands of the dazzling butterflies arrived on Ohio shores to meet a powerful cold front pushing along the lakefront. High winds and rain forced an extraordinary number of monarchs to seek shelter from the inclement weather.” Interestingly, monarchs gathered at Wendy Park ahead of the same storm and strong west winds that led to the roost formation on South Bass Island that this author documented that same night. Approximately 4000 monarchs also formed several roosts at the tip of Point Pelee that evening.
Jen Brumfield often leads boat tours on Lake Erie searching for rare birds. Brumfield reported her monarch observations, explaining “Many, many times I have witnessed monarchs moving over the lake and coming ashore. On the 5th of September 2015, I ran a boat trip off of Port Clinton that covered open water around the Lake Erie islands. I observed 50+ monarchs that day. On September 16, 2015, I counted 250+ monarchs on a 70-mile offshore survey off Vermillion and Huron. The monarchs were anywhere from 5 to 13 miles offshore, and winds were very light from the southwest (virtually no wind). They were flying about 20-60 feet off the water.”
This evidence is corroborated by Jim McCormac of the OH Department of Natural Resources. He was boating on Lake Erie on September 16, 2015, as part of the group tour led by Jen Brumfield. He was able to photograph one of the monarchs, as it flew south over the lake about 6-8 miles offshore. McCormac explained, “The boat left at 8 am, and returned around 3 pm on September 16, 2015. At our farthest, we probably were around 12 miles out from the mainland, nearing the boundary with Canada. It is about 30-33 miles across Lake Erie at this point (Ohio shore to Canada’s shore). Assuming the butterflies left directly from the Canadian shore, they are making a 30+ mile open water transit. There is a possibility they are island-hopping (islands are about 11 to 15 miles west of the westernmost path that our boat took). Even if they are, it’s still an impressive water crossing, but given that we saw butterflies pretty much throughout the area…it would seem to make more sense that they’re straight-lining it from the Canadian shore.”
Another observer, Alicia Wallace, has also seen monarchs over the open waters of Lake Erie. She serves on an educational tall ship, Appledore IV, which often sails the Saginaw Bay and southern Great Lakes. Wallace reported a monarch sighting over waters west of Pelee Island. She states, “We estimated 25 to 50 butterflies flying around the ship for about 30 minutes between 6am and 7am on September 21, 2014. We had just come out of a fog bank when we saw them. They were flying at boom and mid mast level, so about 12 to 45 feet off the water. It was amazing to see so many monarchs in the middle of the lake.” She further reports a more recent sighting, stating “This week (September 21, 2015) I have seen 10-15 monarchs crossing the Saginaw Bay heading south. This has been around noon and they were only 10-20 feet above water.” Detroit River Hawk Watch has also often reported monarchs flying over the water. Jonathan Stein, lead counter, reports they most often see monarchs flying near the water, but at times the monarchs are also seen quite high with the hawks.
Will monarchs cross Lake Ontario, and can they do so successfully?
The reports of monarchs crossing open water over Lake Erie are further supported by reports of monarch sightings and tag recoveries over Lake Ontario. In searching for evidence of such attempted crossings, this author noted a report by Norman Tremblay of Ontario, Canada, cited in the news of the Lepidopterists’ Society in 1979. Tremblay notes, “In mid-September I was at the Lake Ontario shore east of Ajax. It was a warm morning with a mist rising off the lake. There was practically no wind. A great congregation of monarch butterflies lifted from their overnight roosts and slowly formed a huge tumbling ball of butterflies about the size of a ten-acre field. This enormous mass gathered itself into a tight swarm about 100 feet across and started out south across Lake Ontario some thirty feet above the surface of the water. The annual migration was underway.”
In addition to Tremblay’s report, there is evidence provided by Donald Davis of the Monarch Butterfly Fund. Davis has tagged migrating monarchs at Presqu’ile Provincial Park near Brighton, Ontario, Canada. Davis reports, “When there has been little or no wind in the morning in this park, when the lake is calm and smooth, I have seen monarchs fly out over the lake many times. One time I observed a hawk – a larger hawk such as a red-tailed – flying high and momentarily playing with a monarch over the lake. Perhaps trying to grasp it with its talons. BUT…..a most revealing situation and a one-time observation: the winds appeared to be out of the northeast one day at Presqu’ile, and monarchs had flown out over the lake with a tail wind. THEN….suddenly it became quiet….little wind for perhaps a half hour to an hour…and THEN…..the winds that were part of what must have been a huge circle of a rotating wind system suddenly came from the south or south-west, and all of a sudden, hundreds of monarchs were being blown in to shore from out on the lake. What a magnificent sight! A one-time only sighting.” Davis further reports “I have had reports of boaters way out on Lake Ontario observing monarchs flying south. I have had tag recoveries of monarchs released at Presqu’ile and recovered in Rochester, New York…thus I know that the monarchs set out and try to cross Lake Ontario.” Davis’ tag recoveries include wild monarchs tagged at Presqu’ile Provincial Park and recovered at: Otisco Lake near Marietta, New York; Binghamton, NY; Marcellus, NY; Apalachin, New York; Findley Lake, New York; Olean, New York; and Tully, New York. All of these monarchs were tagged during 1985 and 1988 as part of the Urquhart Insect Migration Association tagging program. Five of these recovery sites are southeast of Presqu’ile Provincial Park, while one is southwest and another is just slightly southwest. Davis did not record prevailing winds at the time, but prevailing winds at Presqu’ile Provincial Park in fall are typically from the west or southwest. Interestingly, Ted McDonald tagged a monarch at Port Hope on the north shore of Lake Ontario and it was recovered in Havana, Cuba.
Are monarchs found over Great Lakes waters during the summer?
Ohio State University’s Stone Laboratory staff members have reported seeing monarchs around the Lake Erie islands in summer. Katie Hollenbeck reports, “We see them all the time, flying about 10-15 feet off the water.” Naturalist Jackie Taylor of the Lake Erie Islands Nature and Wildlife Center has documented monarchs reproducing in the islands for the last four years. She reports, “We usually see our first monarchs beginning in late June. Then we see fall migrants move through the islands in mid-September, flying about 20-30 feet over the water between the islands. The southwest tip of South Bass Island is a favorite rooting site for migrating monarchs.”
A very interesting report of summer monarch activity comes from Dave Agazzi, captain of a fishing charter boat on Lake Michigan. Agazzi has been boating on Lake Michigan for 20 years. He sees monarchs in fall, usually in the afternoon boat trips and flying west or southwest. But on July 19, he was stunned to see a huge influx of insects while on a charter from 1:30 to 6:30 pm. The wind was calm, and they were getting bit by flies and seeing insects they had never seen before. Agazzi noted that one monarch flew by about every 1-2 minutes for the five hours he was on the water, headed due west. He was 10-11 miles offshore from Kenosha, WI. The monarchs never landed on the boat, but came close enough that he was certain of their identification. They were flying fast, about 8-20 feet off the water. Red admirals were also flying, and Agazzi described them as also flying fast but more erratically than the monarchs. Dr. Chip Taylor explained the nature of Agazzi’s observation, stating, “This is evidence indicating the beginning of the premigration migration.”
The premigration migration has also been witnessed by this author in the Lake Erie islands, usually during the first two weeks of August. See this article on this author’s premigration experience during August 2013 on South Bass island www.mlmp.org/Newsletters/monthly/2013/mlmp_update_201308-201309.pdf
So if monarchs can cross Lake Erie, how might they do it?
The flight threshold for monarch butterflies is a thoracic temperature of 55F (Masters, Malcolm & Brower, 1988). Ambient temperatures, along with wind speed and cloud cover conditions, must be suitable to allow for sustained flight across the lake. Notably, lake waters cool much more slowly than surrounding air over land. Surface water temperatures in September for Lake Erie and Lake Ontario range from the high 60s to low 70s. Robert LaPlante, meteorologist for the National Oceanic and Atmospheric Administration and National Weather Service based in Cleveland explains, “Warm air over Lakes Erie and Ontario is present from the middle of July until the middle of October. By mid-October the average surface water temperature has dropped to the mid to upper 50s. During the third quarter of the year (fall), the warm lakes keep the lower few thousand feet of air usually above 60 degrees. The warm air could give monarchs buoyancy over the lake. Sometimes at night there is convergent wind flow of offshore breezes that could produce upward motion over the lake. We could get a line of cumulus clouds and perhaps waterspouts. Lake Erie being the shallowest and the farthest south, gets the warmest of all the Great Lakes so the nocturnal warming or less cooling of the near surface air would be most pronounced over it.” LaPlante further explains, “On a typical sunny day, there normally would not be much rising motion over the lake because it is typically absorbing energy from the sun. During the late summer and early fall, the lake is warmer than the air over the land in the morning so there could be thermals–but what typically happens is that a land or offshore breeze develops at night that moves out over the water and may converge over the center of the lake. This process then reverses in the morning, as the land begins to warm and an onshore breeze develops.” In summary, these warmer air temperatures over the lakes would be sufficient to allow for flight.
Lake Erie can be 30 to 50 miles across. Monarchs could cross that distance using a combination of powered flight and gliding flight. Dr. Chip Taylor explains, “With appropriate cross winds from the northwest, monarchs would get lots of lift and though drifting southeast, would be able to maintain themselves above the surface with minimal effort–a flap, flap every twenty or thirty feet or so. Monarchs have a 3 or 4 to one glide ratio. Meaning that once they gain altitude they can glide 3-4 feet forward for every foot they lose in altitude. If there are tail or quartering winds and the air temperature above the water is high enough–ideally in the mid to high 60s–they should be able to maintain flight with a minimal effort.”
Basking monarchs in roost at South Bass Island 2015. Photo by Candy Sarikonda.
What we know and don’t know about monarch movements over Lake Erie
Based on observations by myself and naturalists in the Lake Erie islands, and reports from other citizen scientists in the region, it is clear that monarchs do cross the open waters of Lake Erie. They do so during the summer, as well as in the fall. They are most often seen flying at 20-60 feet above water, but reports of flight altitude range from 8-100 feet above water. Since most observers cannot see beyond a height of 300 feet above them, it is not clear if monarchs may be migrating over the lake at higher altitudes. Glider pilots have seen monarchs at 10,000 feet, and helicopter pilots servicing oil rigs in the Gulf have seen them at 1000-1200 feet. Are monarchs flying at altitudes over 300 feet above Lake Erie? More evidence is needed. Mark Shieldcastle, Research Director for the Black Swamp Bird Observatory, recently reported seeing monarchs fly onshore from Lake Erie routinely at 100 to 200 meters altitude, along the Magee Marsh beach area on the southern shore of Lake Erie. Additional reports such as this will provide valuable information for understanding the altitude of the monarch migration over Lake Erie.
Monarchs have been seen by naturalists and citizen observers gathering in roosts at Point Pelee, South Bass Island and Wendy Park in response to approaching storms and strong sustained winds. Most often, monarchs gather in roosts awaiting warmer weather and calmer winds to continue their migration. Northerly winds facilitate this migration. Notably, monarchs will fly out over the lakes from shore with northerly winds, but they will also fly out in a southerly headwind, suggesting they are deliberate in their attempts to fly across the lake. Their flight during the fall migration is most often reported as southward across the lake, as reported by observers in the present day as well as the Southey Shoals lighthouse keeper in 1937-1938. How winds might affect their flight direction over the open water will need further study. It will be important to document body vector (the monarch’s intended flight direction), in relationship to the monarch’s vanishing bearing (the actual direction of its flight).
How winds affect monarch flight behavior is a subject of study now being undertaken by the Marine Monarchs project. Dr. Chip Taylor and Dr. Tracey Villareal have partnered on the project, with the goal of documenting monarch flight behavior over land as well as on water. An app has been created that will allow observers, both on land and water, to record the vanishing bearings and body vectors (headings) of migrating monarchs. To record the bearings and headings the observer positions him or herself directly behind a monarch that is heading away from the observer. By lining up the compass indicator of the app with the long axis of the departing butterfly and touching the tab, the app reads and records the compass direction indicated by the long axis of the butterfly’s body. The vanishing bearing is the compass heading observed as the butterfly disappears from view. Cross-winds will cause the butterfly to drift to the right or left of the intended heading. True headings are most effectively recorded when there is no wind. When the app is complete, each observation will be linked to a site that provides the current wind speed and direction as well as temperature and cloud cover. By recording flight vectors and vanishing bearings throughout the migration under a variety of physical conditions, it should be possible to establish how monarchs respond to these conditions and to obtain a better understanding of how they reach the overwintering sites in Mexico.
If you see monarchs migrating, PLEASE report your sightings to Journey North. Get involved in the Monarch Watch tagging program. Check the Apple App Store for the new Marine Monarchs app (Monarch Migration – Tracking Monarch Butterfly Migration), and consider participating in this new project to document the monarch migration over land and water. Your reports of monarch migratory behavior are needed to unlock the many mysteries of the monarch migration over water!
Resources and References
Journey North news update: Peak for Great Lakes http://learner.org/jnorth/monarch/fall2015/monarch-butterfly-migration091715.html
Point Pelee National Park monarch information http://www.pc.gc.ca/eng/pn-np/on/pelee/natcul/natcul5/~/media/pn-np/on/Pelee/natcul/Monarch%20fact%20sheet%20ENG.ashx
Lake Erie Islands Nature and Wildlife Center newsletter articles regarding monarch migration and reproductive activity in the islands http://lakeerieislandswildlife.com/?page_id=366
Photos of monarch roosts on South Bass Island, 2014 https://www.flickr.com/photos/candy__kasey/albums/72157647561394606/with/15220175266/
Photos of monarch roosts on South Bass Island, 2015 https://www.flickr.com/photos/candy__kasey/albums/72157658183044290
Surface water temperatures for Lake Erie and Lake Ontario
Marine Monarchs project https://sites.cns.utexas.edu/marine_monarchs
Climatic wind data for the U.S. http://www.ncdc.noaa.gov/sites/default/files/attachments/wind1996.pdf
Muscular thermogenesis, flight threshold in insects found in
Hoffmann, K. H. (1985). Environmental physiology and biochemistry of insects. Berlin: Springer-Verlag.
Beall, G. 1941. The Monarch butterfly, Danaus archippus Fab. II. The movement in southern Ontario. Canadian Field-Naturalist (Ottowa) 55:133-137
Brower, L., Fink, L., & Walford, P. (2006). Fueling the fall migration of the monarch butterfly. Integrative and Comparative Biology, 1123-1142.
Gibo, D., & Pallett, M. (1979). Soaring flight of monarch butterflies, Danaus plexippus (Lepidoptera: Danaidae), during the late summer migration in southern Ontario. Can. J. Zool. Canadian Journal of Zoology, 1393-1401.
Gibo, D. (2011). Altitudes attained by migrating monarch butterflies, Danaus p. plexippus (Lepidoptera: Danaidae), as reported by glider pilots. Can. J. Zool. Canadian Journal of Zoology, 571-572.
Masters, A., Malcolm, S., & Brower, L. (1988). Monarch Butterfly (Danaus Plexippus) Thermoregulatory Behavior and Adaptations for Overwintering in Mexico. Ecology, 458-458.
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