Brian, It is interesting to see how many different species raise Cowbird chicks. According to the species account in Birds of North America Online, one comprehensive source found that Yellow Warblers are the most frequent host species for Brown-headed Cowbirds. At home here in Maryland, I see Song Sparrows (which are the number two most frequent host species) feeding Cowbird chicks in our yard every summer.
The largest size disparity I have ever witnessed was a tiny Ruby-crowned Kinglet feeding a significantly bigger Cowbird chick in Rocky Mountain National Park. Jim Nelson Bethesda, Maryland From: [email protected] Sent: Monday, June 27, 2016 1:49 PM To: Colorado Birds Subject: [cobirds] Yellow Warbler and Cowbird, Arapahoe County Today while walking along my favorite part of the Mary Carter Greenway I encounter an odd looking bird that I could not figure out. It was all brown with fine streaks along the breast and belly but the bill was wrong for a finch and it was too big. Then I noticed it was flapping around from branch to branch frantically, and I noticed it was chasing a yellow warbler male and constantly calling. I could not make sense of why this bird would be chasing a warbler and calling like that. Finley both stopped on a Russian olive branch and I was able to get a better view. I observed the warbler glean an insect (likely a gnat) and take it lower down to the unknown bird and stick it in the bird’s mouth. It finally came together then. This was a recently fledged juvenile brown headed cowbird that the warbler believed to be its offspring. It was certainly dwarfed by the cowbird. I have not seen this in the wild before, I have one nature programs but that was it. Interesting behavior to watch, not all that good for the warblers however. Hopefully their population will not be to affected by this along the river. This was at the mile marker 12, the dirt walking path goes through some woods that is a favorite for warblers and other birds. Thought I would share this. Brian Johnson Englewood CO -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/e6a087cd-2a5e-475a-ae68-035ce6e3d871%40googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/880480934A114201BE5F208CA72F45EC%40jimPC. For more options, visit https://groups.google.com/d/optout.
