There have been several questions brought up lately about Brown-headed Cowbirds, so I decided to provide some information about these interesting birds. As luck would have it, a pair of cowbirds showed up to bathe in my birdbath, staying around long enough for me to get some photos including this one. Notice it’s the male that sports the brown head and black body, while the female is all over grayish brown. She also has light streaking on her front, which you can just make out in the photo.

Brown-headed Cowbirds are brood parasites, which means they lay their eggs in other birds’ nests. During breeding season, female cowbirds will remove an egg laid by the host mother and lay one of her own eggs in its place. Cowbirds can lay nearly one egg a day, which can number up to 40 eggs in a season! The host parents don’t recognize that the egg is not their own. When it hatches, they see a hungry chick begging for food and they oblige.

If the cowbird lays her egg in a nest of a smaller bird, this can have dire consequences on its nest mates who may not get fed as well as the larger cowbird chick, and they may not survive. There are exceptions – if a cowbird lays her egg in a goldfinch or House Finch nest the cowbird will not survive because it requires a diet rich in insects. Goldfinches and House Finches are strictly vegetarian and will never feed their chicks insects.

Now you may be asking, don’t mother birds recognize that the cowbird egg isn’t theirs and toss it out? Surprisingly, most don’t but there are a few exceptions including Gray Catbirds and Yellow Warblers. Catbirds will toss the foreign egg out of their nest, but Yellow Warblers are too small to do this. Instead, they build a second nest on top of the first and hope the cowbird doesn’t return and lay another egg.

Speaking of catbirds, they are aptly named after the catlike mewing call they make. So, does that mean cowbirds moo? Nope, in some areas, cowbirds are known for their habit of following herds of cows in search of insect prey that get stirred up as the animals walk, hence the name cowbird. Makes sense, but personally I think it would be more fun if they mooed!