Re: [cobirds] Cassin's Kingbird origins

David and all,

The map in Sibley is not accurate.  There are breeding populations in eastern Montana, southwestern SD, eastern WY and western Nebraska (Wildcat Hills, etc.).  Birds of Nebraska by Sharpe et al list them as "fairly common breeders in the Panhandle".  Birds of Wyoming by Faulkner reports a count of 31 at Pine Bluffs on 3September2000.  Most of these areas have open grown ponderosa pine which looks a lot like the eastern Black Forest in Elbert and that is where I always figured our late September-early October Cassin's at places like the Pawnee Grasslands and Fort Collins come from.  There is also a patch of aberrant limber pine just south of where CO-NE-WY come together in CO that is private but may also support a breeding population.  Cassin's Kingbirds show up on the northeastern plains and along the Front Range pretty much every year about this time of year (later than Eastern and Westerns).  There seems to be more of them this year than most, but then, there are a lot more birders than there used to be.  I think the Cassin's Kingbirds are coming from somewhere north of us.

Dave Leatherman

Fort Collins

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From: cobirds@googlegroups.com <cobirds@googlegroups.com> on behalf of David Suddjian <dsuddjian@gmail.com>
Sent: Wednesday, October 4, 2017 3:45 PM
To: Colorado Birds
Subject: [cobirds] Cassin's Kingbird origins

 

I'll suggest an answer to my own question about where the recent Cassin's Kingbirds are coming from. I suggest this is a northward movement, similar to the "reverse" migration of Tropical Kingbirds in California, and now one from CO.  Looking at eBird patterns for Wyoming and Nebraska to the north, and CO counties that are north of or adjacent to the main CO breeding range of Cassin's (e.g., Jefferon, Boulder, Larimer, Weld, Adams), there is an increased frequency of occurrence in September that is not a continuation of a late summer presence but seems to result from migrants moving during September (and into early October). Since there is not really a pool of birds to the north during September or late August, it seems to me most likely that the Cassin's we are finding over the last few weeks have moved north in a "reverse" pattern... maybe from afar away.

Maybe this pattern is already obvious to others or established? Thoughts?

David Suddjian

Ken Caryl Valley

Littleton, CO

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