Female Cowbird: Notorious Nest Invaders

A female cowbird is a dull looking bird with plain plumage that is easy to miss in the backyard. But there's a really important reason for that.

Female brown-headed cowbird at feederCourtesy Christal Knight
Female cowbird

How to Identify a Female Cowbird

Question: I’ve lived in this house for 20 years and I’ve never seen this bird before. What could my new yard bird be? —Christal Knight of Palatka, Florida

Kenn and Kimberly: One of the most subtly colored birds in North America, lacking any distinctive pattern, the female brown-headed cowbird is a frequent source of confusion for birders. It’s easy to overlook, too. The females have a good reason to be inconspicuous: They lay their eggs in the nests of other birds, sneaking in quietly while the nests’ owners aren’t looking. A female cowbird is easiest to see when they come to a feeder, as in your photo. The short, thick, pointed black bill ending at a flat forehead and overall plain, dull grayish-brown look are the best field marks for recognizing them.

Male brown-headed cowbirds are more noisy and noticeable. Check out 5 types of blackbirds you should know. Plus: Take a quiz to see how many female birds you can identify.

juvenile cowbirdCourtesy Julia Worth
Chipping sparrow feeding a young cowbird

Cowbird Eggs

Female cowbirds are brood parasites. They don’t build nests or tend to their own young. Rather, they employ what seems to be an unfair strategy of laying eggs in the nests of other birds, such as the chipping sparrow. The adoptive adults hatch the cowbird eggs, unaware they aren’t the biological parents. These unwitting foster bird parents then care and feed the young cowbirds.

Female brown-headed cowbirds sometimes produce more than 24 eggs in a single summer. Cowbird eggs have been found in nests of more than 220 other species.

It can be tough to see a small songbird feeding the much larger young cowbird, but it’s very important not to interfere. Cowbirds are a native species, protected by law. They do create conservation challenges for some species, such as Kirtland’s warbler, but in general nature manages to maintain a fair balance.

Although cowbirds are a parasitic pain for bird parents, some birds have figured out ways to successfully deal with them. Catbirds, for example, usually recognize their own eggs and toss out any interloper eggs they find in their nests.

Next, learn how to keep house sparrows out of bluebird boxes.

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Kenn and Kimberly Kaufman
Kenn and Kimberly are the official Birds & Blooms bird experts. They are the duo behind the Kaufman Field Guide series. They speak and lead bird trips all over the world. When they're not traveling, they enjoy watching birds and other wildlife in their Northwest Ohio backyard.