Yellow warblers are well documented for recognizing a cowbird egg in their nest. They will build a new nest on top of the nest with the cowbird egg. I've seen photos of 4 or 5 complete nests in a stack. That's one way to not raise any cowbird young, but maybe not raise any of your own either! They obviously raise cowbird chicks now and again though.
I saw Blue-gray Gnatcatcher feeding a cowbird chick on Jekyll Island GA many years ago. Just about as big of a disparity as a kinglet. Scott Somershoe Littleton CO Scott Somershoe Co-Author of *Birds of Tennessee: A New Annotated Checklist <http://www.amazon.com/Birds-Tennessee-New-Annotated-Checklist/dp/1507815751/ref=tmm_pap_swatch_0?_encoding=UTF8&qid=1453317221&sr=8-3>* On Mon, Jun 27, 2016 at 12:20 PM, Jim Nelson <[email protected]> wrote: > 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 <[email protected]> > *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 > <https://groups.google.com/d/msgid/cobirds/e6a087cd-2a5e-475a-ae68-035ce6e3d871%40googlegroups.com?utm_medium=email&utm_source=footer> > . > 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 > <https://groups.google.com/d/msgid/cobirds/880480934A114201BE5F208CA72F45EC%40jimPC?utm_medium=email&utm_source=footer> > . > 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/CAJmtx%2BWK6wuZzyXxextvVwKJxT1Dnk5mvsj9_1Ro%2Bcv9eLVERA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
