Yesterday evening, before sunset, a flock of cowbirds landed on my porch. They stood on the rail for a few minutes. Just long enough for me to confirm my identification. Some of them looked like finches, all streaky, but I now believe they were juveniles, or perhaps females.
These blackbirds are brood parasites. The females lay their eggs in other birds' nests. This allows them to produce a lot of eggs (up to 36 per season!), since they don't have to take care of them or the hatchlings. Forced adoption, which might well result in the killing of some of the legitimate nestlings. [Side note: If you search online, you can find images of large cowbird chick with its small colorful adoptive parent.] Most bird species do not realize they have an invader, but some, like the Yellow Warbler, can, but they are too small to push the large cowbird egg. So instead, they build a new nest on top of the old one (allaboutbirds.org).
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