Sunday, July 8, 2012

Warbler Guy, which warbler may disperse &/or migrate by July? Which eastern warbler species is a likely West Coast vagrant?

Heather (in Seattle) one good candidate as an answer to your questions is the Tennessee Warbler (photo shown here).

In the USA's East and Midwest where this species is typically seen, its early dispersal away from natal/nesting areas is common. Many upper Midwest states have August banding records of Tennessee Warbler individuals away from their nesting grounds. 

But migration patterns may vary from one year to the next. That's because annual numbers for Tennessee Warbler often correlate with the the intensity of the summer season's spruce budworm output (that is a cyclical phenomenon in the boreal forest habitat where many breed). 

Interestingly, Heather, some females arrive on northern breeding grounds in the spring already pregnant due to mating that occurs during daytime layovers in migration. In non-breeding season habitat, Tennessee Warbler is often seen eating nectar and fruit. 

For me, the autumn in northern California where I live includes spotting an occasional Tennessee on a cloudy or foggy day amid small refuge patches of non-native Monterey Cypress within a west Marin County national park, Point Reyes National Seashore. That's because this species is one of the most typical vagrant eastern wood-warbler species to appear in the West.

(Photo by Corey Finger)

By contrast, in the spring, during my annual spring jaunt to the Midwest, I'm often sweating by noon while watching the same species in northern deciduous hardwood habitat. There, it’s a common transient through Door County, a northern Wisconsin environ that hosts 16 to 18 nesting warbler species as the farthest southern terminus expression of boreal forest in the lower 48 USA states.


Anonymous said...

I never understand why TN Warbler is named as such because it's never nesting in TN.....

Anonymous said...

Thanks for the blog.....C.R.

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