Date: 5/4/18 7:13 pm
From: Ted Floyd <tedfloyd57...>
Subject: [cobirds] Let's document Myrtle x Audubon's Warblers in Colorado
Hey, all. Earlier this Friday evening, May 4, I saw a couple of Myrtle x
Audubon's Warblers at the University of Colorado South Campus near Tantra
Road, Boulder County. Which got me to thinking about something...

Away from the breeding grounds, Myrtle and Audubon's Warblers co-occur
across a huge swath of western North America, easily a million square
miles. Yet *The Sibley Guide* informs us that hybrids are rarely detected
away from the breeding grounds. I have no reason to doubt the overall
accuracy of that statement, but I also note that, at least here in eastern
Boulder County, hybrids (or intergrades, if you prefer) are legion.

Here's the deal. Even though Myrtles and Audubon's spread out across a vast
region when they're not breeding, that's not necessarily the case for their
hybrids. By analogy, consider the enormous winter range of the Dark-eyed
Junco vs. the quite limited range in winter of White-winged Junco.
(White-winged Junco in winter occurs chiefly in the ponderosa pine belt of
the Colorado Front Range.) I wonder if Myrtle x Audubon's hybrids are
similarly range-restricted. For what it's worth, I never knowingly saw a
Myrtle x Audubon's hybrid in all my years of looking at Myrtle and
Audubon's warblers in New Mexico (1992-1994) and Nevada (1999-2002).

It would be cool if we could say with some precision where Myrtle x
Audubon's warblers go when they're off the breeding grounds. Definitely
here in eastern Boulder County! But how much more extensively?

Here's a photo of one of the hybrids I saw this evening:


What to do? Easy! Put it all on eBird.

Ted Floyd
Lafayette, Boulder County

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