How big is the western fall migration going to be this year? I've been getting mixed messages from what I've been observing in the field so it's kind of hard to say.
1) Monarch caterpillars and even chrysalids have been easier to find at the milkweed patches I've checked in northern and central California in recent weeks as compared to most prior years.
Reference map of the locations of milkweed patches where larvae or chrysalids were seen:
http://i959.photobucket.com/albums/ae78 ... gpinel.jpg
a) A little southeast of Placerville, Calif. at 1,750 feet elevation along Mt. Aukum Rd and 1 mile south of the town of Somerset, I saw this chrysalis on speciosa milkweed on Sept. 10 and 13:
http://i959.photobucket.com/albums/ae78 ... gpinej.jpg
b) A little west of Placerville on Motherlode Drive in the town of El Dorado, Calif. at 1,500 feet elevation I saw this caterpillar on fasicularis milkweed on Aug. 20:
http://i959.photobucket.com/albums/ae78 ... gpinei.jpg
c) On Sept. 11 at Coleville, Calif. south of Lake Tahoe and east of the Sierra Nevada crest I saw this monarch caterpillar at 5,200 feet:
http://i959.photobucket.com/albums/ae78 ... gpineh.jpg
d) On Sept. 13 a few miles south of Bridgeport, Calif. at 6,650 feet I saw this and another monarch caterpillar: http://i959.photobucket.com/albums/ae78 ... gpineb.jpg
Incidentally, these sightings of caterpillars at these high elevations in mid-Sept. refutes the suggestion that Shawna Stevens and Dennis Frey made in their recent paper where they said it was
probably "too cold" in August and Sept for monarch caterpillars to complete their development:
1) So far I havn't seen any fall migrant monarchs in diapause yet nectaring on my backyard butterfly bushes near Placerville, Calif. In a good year, several per day would be present during the first two weeks of Sept.
2) On Sept. 11-13 when I visited the Bishop and Big Pine areaa of the northern Owens Valley of Calif. (a major monarch breeding area) I saw only modest numbers of monarchs (5 in Big Pine and 2 in Bishop) and most of them were reproductive individuals rather than fall migrants in diapause:
http://i959.photobucket.com/albums/ae78 ... gpinea.jpg
http://i959.photobucket.com/albums/ae78 ... gpineg.jpg
http://i959.photobucket.com/albums/ae78 ... gpined.jpg
http://i959.photobucket.com/albums/ae78 ... gpinef.jpg
So overall I'm not too confident that the size of the overwintering colonies along the coast this fall is going to be much bigger than the ultra low numbers we saw last winter. However, we won't know for sure until around Oct. 5.