Monarch Butterflies and Milkweed in Oregon

[Mona Miller]

Cross Posting Message with permission from NorWestLeps from Dr. David James, Washington State University:

"This season will provide us with the best opportunity for some years to learn more about Monarch migration to and from the Pacific Northwest.

Low density overwintering populations in California naturally translate to low numbers of Monarchs reaching northern Oregon, Washington, Idaho and southern British Columbia. This has been the case for many seasons now and summer breeding populations in the PNW have been tiny or nil.

However, the large overwintering populations seen in CA this winter may result in far more Monarchs heading our way than 'normal' and we could see good use of our abundant milkweed resources in E WA, E BC and ID by breeding populations in July-August.

Thus I would appreciate reports from people seeing Monarchs in northern California-southern Oregon over the next 4-6 weeks so we can be ready to monitor their spread through WA, ID and BC. A plan to conduct a tagging program this season in WA is in the works, but I'll share more about that later.....

More milkweed in Oregon would certainly help Monarch populations by providing additional breeding habitat for spring migrants but the new generation (one removed from the overwintering generation) that migrates from northern and central California to the PNW in May and June, responds strongly to increasing daylength by flying north-north-westward at a rate of many miles per day. They are on a mission to travel as far as they have to to find milkweed! The 250-300 mile N-S extent of Oregon can be traversed by a migrating Monarch in less than a week (under sunny skies). More important (to successful migration) is likely to be the availability of nectar plants. Once Monarchs reach eastern Washington and eastern British Columbia and Idaho, they find plenty of Showy (and narrow-leaved) Milkweed."

David

Dr David G James
Associate Professor of Entomology,
Washington State University,
Prosser, Washington 99350
USA
Respond to: david_james |at| wsu |dot| edu [convert to normal email by exchanging at for @ and dot for . no spaces.]