|Photo by Paul Cherubini 11-12-13 Pismo Beach (Used with permission)|
|Photo by Paul Cherubini|
You've likely seen the migration maps - monarchs from Arizona fly mainly to Mexico and a few fly to California. Yet those California sightings come in clusters. In 2008, five Southwest Monarch Study tags were spotted: Three in San Diego and two in Ellwood Main in Goleta. The photos of the tags from San Diego were fuzzy and the numbers unreadable. At first we thought there was only one in Ellwood Main but when we finally had a photo of the tagged monarch with the number clearly identified we realized the tag was in a different place on the wing than the earlier photo. In 2009 there was one spotted by Monarch Alert. Then none.
|Canelo Monarchs 10-15-13|
|One of the weather charts Darcy shared|
"Basically what I've found from the Tucson upper air soundings is that there were southeast winds during the September 15 - 20 time frame, at a relatively low atmospheric level, that could have "propelled" the two (now three) monarchs retrieved in CA. During the same time period, there were winds at slightly higher atmospheric levels from the NW and N that could have resulted in monarchs being propelled to Mexico from the same AZ area. It would all depend on the altitude of their flight. I think that will be the case for most CA sightings."
As we talked, Darcy shared copies of the Atmospheric Soundings for the time period to explain her findings. We realized that so far, every California recovery had strong lower level winds so we can not rule out wind as a driving factor in migration destination. Keep in mind if a monarch can ride a thermal high into an unstable air mass and punch through the atmospheric lid of the wind sheer layer above it is conceivable that we could tag two monarchs on the same day, and have one recovered in California and one in Mexico. By late September and early October, the time of our peak migration in Arizona, winds tend to settle into a more typical Westerly direction. So far all of our recoveries from that period are in Mexico.
Darcy offered to keep daily weather maps every September, the time our monsoon season is likely the most unstable, to track weather phenomena in relation to the monarch migration in Arizona. Eventually we will publish this information after more data are available to see if this pattern persists. Amazing how our love affair with monarch butterflies and their fascinating migration could help us uncover and learn so many new things!