"Centuries ago this bird probably followed bison herds on the Great Plains, feeding on insects flushed from the grass by the grazers. Today it follows cattle, and occurs abundantly from coast to coast. Its spread has represented bad news for other songbirds: Cowbirds lay their eggs in nests of other birds. Heavy parasitism by cowbirds has pushed some species to the status of 'endangered' and has probably hurt populations of some others."
Mr. Swainson has well remarked,¹ that with the exception of the Molothrus pecoris, to which must be added the M. niger, the cuckoos are the only birds which can be called truly parasitical; namely, such as 'fasten themselves, as it were, on another living animal, whose animal heat brings their young into life, whose food they live upon, and whose death would cause theirs during the period of infancy.'
1 Magazine of Zoology and Botany, vol. i. p. 217.
"Journal of Researches into the Natural History and Geology of the Countries Visited During the Voyage of H.M.S. Beagle Round the World, 1832-36" - Charles Darwin
Cowbirds commonly invite birds of other species to preen them, but occasionally an interspecies encounter includes homosexual mounting when a House Sparrow is involved.
"Biological Exuberance: Animal Homosexuality and Natural Diversity" - Bruce Bagemihl
“Perched gracefully, the Brown-headed Cowbird enjoys a moment of rest.” - Copilot
I watched this brown-headed cowbird (Molothrus ater) for about an hour lounging around my backyard. Some people don't like these birds because they are "obligate brood parasites," meaning that the female lays her eggs and the nests of other species and depend on the other birds to raise their young. But I think it's just part of nature, a circle of life sort of thing. For them, "it is the way." ;-)
"Some birds, such as the Yellow Warbler, can recognize cowbird eggs but are too small to get the eggs out of their nests. Instead, they build a new nest over the top of the old one and hope cowbirds don’t come back. Some larger species puncture or grab cowbird eggs and throw them out of the nest. But the majority of hosts don’t recognize cowbird eggs at all." -allaboutbirds.org
Brown-headed cowbirds are parasitic egg-layers, meaning they lay their eggs in the nest of other birds so they don’t have to lose energy raising the young themselves. This is why I also didn’t seen any adults nearby. I think it might have been cared for by a chipping sparrow or song sparrow, as those birds were close by.
From the top: male White-throated sparrow (Zonotrichia albicollis) and female Northern Cardinal (Cardinalis cardinalis), male Red-winged blackbirds (Agelaius phoeniceus) and male Common grackle (Quiscalus quiscula), male Northern Cardinal (Cardinalis cardinalis) and male Mourning dove (Zenaida macroura), male brown-headed cowbirds (Molothrus ater), male Red-winged blackbirds (Agelaius phoeniceus), male Mourning dove (Zenaida macroura) and female brown-headed cowbird (Molothrus ater), Blue jays (Cyanocitta cristata), male Mourning dove (Zenaida macroura) and male brown-headed cowbird (Molothrus ater)