With regret, I have had to cancel the Monarch Tagging Day planned for this Saturday August 22nd.
During the past two days I’ve spent about 6 hours at the site finding only about 6 Monarch per hour. Only half of these are potential migrants (worthy of tagging), the remainder are aging breeders who will not be migrating. In 2014 when we held the tagging day on August 23, the pre count was around 22 (mostly migrant) Monarchs per hour.
This is the first year since I’ve been studying the Monarch population at this site that numbers have fallen in August and as I suggested in previous emails I think this can be attributed to the 16 day heatwave that coincided with the emergence of the first locally produced generation. I have now had the chance to look at the temperature data in more detail.
A WSU Agweathernet climate recording station is present just 2 miles from the Monarch site and this showed that the average maximum temperature during June 26-July 10 was 103.1 F ! Every day during this period exceeded 100 F with a maximum of 109 on June 28.
These temperatures exceed optimal temperatures for Monarchs by a significant margin and appear to have had a detrimental effect on population development and survival.
I’m sorry for this disappointing outcome but look forward to a better season in 2016 and hopefully a Monarch Tagging Day on the third weekend in August!
Dr David G James
Associate Professor of Entomology
Washington State University
Prosser, Washington 99350