Date: 6/21/17 7:55 pm
From: Kimberly G. Smith <kgsmith...>
Subject: the end of the cowbird string - maybe
I am attempting to stop this string, but by offering more information, I may allow it to continue... :)

Species are either acceptors or rejecters... this has been known for many years due to the pioneering work of Herbert Friedmann, who published "Host relations of the parasitic cowbirds" in 1963...
https://archive.org/details/hostrelationsofp00frie

Of course, his publication predates the release and expansion of House Finches in the eastern US but they appear to be acceptors based on his information...

Acceptors do not recognize cowbird eggs as different from their own... rejecters do and either eject the cowbird eggs, abandon the nest, or build a new nest on top of the nest with cowbird eggs (e.g. Yellow Warblers)

Re habitat change: Cowbirds have to have somewhere to feed... their preferred feeding areas are associated with livestock, preferably horses but cattle feedlots will do... for example, there is almost no cowbird parasitism in the forests of the Ozarks... every study we have done on nesting success has had no effect by cowbirds... but apparently they are finding feeding areas in urban environments...

The best study of this is by Jared Verner who documented the colonization of the Sierra Nevadas by cowbirds as the horse tourism trade expanded into that area... I can supply references if you are interested

So habitat change per se is not the issue, it is habitat changes that allow cowbirds to find feeding areas...

Cheers, Kim

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Kimberly G. Smith
Distinguished Professor of Biological Sciences
Department of Biological Sciences
University of Arkansas
Fayetteville, AR 72701
Phone: 479-575-6359 fax: 479-575-4010
Email: <kgsmith...><mailto:<kgsmith...>
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