By Celeste Silling
Here at Gulf Coast Bird Observatory, it’s cardinal season. For every ten birds I see on our bird feeder, about nine of them are Northern Cardinals, and many of those are fledglings. The parents stay with the fledglings, and they often visit the feeder as a family unit, with the parents breaking open sunflower seeds for their babies. But one member of these cardinal families is not like the others… because she is a Brown-headed Cowbird.
The Brown-headed Cowbird is a native Texan songbird with a knack for crime. These birds do not build nests, nor do they incubate their own eggs. Instead, females lay their eggs in the nests of other birds, then leave. They do this presumably without the other bird’s knowledge, tricking the nest owner into incubating the new egg and raising it as their own.
This tactic is known as brood parasitism, as the baby cowbird is a parasite to its new parents, the hosts. The host birds use significant time and energy raising this stowaway, often at the expense of their own chicks. Sometimes the cowbird baby will even push the other eggs and chicks out of the nest, allowing it to get more food and attention.
This life of crime might seem strange, but it ultimately benefits the cowbirds. While other mothers are building nests, incubating, and bringing food back to their babies, the cowbird mother is simply laying eggs. By placing her babies in non-stop daycare, she is able to lay up to three dozen eggs per season while other songbirds lay closer to six.
As for the host birds, different species have different reactions to the interlopers. Some birds never realize that their baby isn’t their own, and some realize too late. Species such as the Yellow Warbler can recognize cowbird eggs but are unable to get the large eggs out of their nests. Their solution is to call it a loss and build a new nest over top of the old one. Some other species can puncture or throw out the cowbird eggs. But Brown-headed Cowbird eggs have been found in the nests of more than 220 species, and not all of them can notice or fight back.
The cowbird that I see feeding with the cardinals at our feeder does not seem particularly malicious. She likes to feed with the cardinals, but doesn’t beg for food, and hasn’t been bullying the cardinal chicks. The cardinals don’t seem to have a problem with her either, allowing her to feed with them, and even perch and rest together.
While this might not be an odd sight in the bird world, it’s still exciting to see a cowbird in amongst its host family. Male Brown-headed Cowbirds have black body feathers and a dark brown head. The females are plain brown with fine streaking on the belly. Fledglings are brown and streaked, with light feather tips. So, if you see an odd brown bird in amongst the families on your feeder, you might have a cowbird of your own! Keep your eyes peeled!
Photo caption: A Brown-headed Cowbird and young Northern Cardinal together at a seed feeder.
Photo credit: Gulf Coast Bird Observatory
