[cobirds] Where do Juncos go in the summer?

My post to Cobirds was a response to a question posed on 

the Douglas County list serve by Scott Sorenson.

Here is his original inquiry. (I apologize for any confusion).

Joe Roller, Denver

Question on Juncos

I live in the North Pinery and see Dark-Eyed Juncos all winter long.  Sometimes 15+ at a time are scurrying about below my feeders.  I see the Oregon, Slate-colored, and Gray-header variants. This winter for the first time I believe I spotted the Pink-sided variant as the pink sides touched on the lower breast.  In the last two weeks, they have all but disappeared. 

Do they all head to the mountains?  I have a cabin in the Granby area where I see the Gray-headed all summer but rarely the other variants.  Do the variants tend to flock together?  When they breed do they tend to select their own variant?  I figure they must be fairly variant-selective or the distinctive variants would blend into a continuum.  How did the variants begin?  Were they geographically separated long enough to evolve into separate color variants but not long enough to be a different species?  Or do they inter-breed freely and just happen to result in one of four major color variants?  

A side note, a couple of summers ago I saw what I believe was the Mount Evans variant at my cabin near Granby. 

You can see that watching these little guys all winter has peaked my curiosity.  

Thanks for any insight you may have.

Scott

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Scott Sorenson

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