Brown-headed Cowbird

Common Name: Brown-headed Cowbird.

Scientific Name: Molothrus Ater.

What to look for?  Brown head! And the subtle brown head sits atop the adult male’s glossy black plumage. The female Brown-headed Cowbird is plain brown with the head and underparts lighter in tone. The bill of a Brown-headed Cowbird has a distinctive shape. It is much shorter and thicker-based than other blackbirds', almost finch-like at first glance.

Where can they be found at Carillon Stonegate Pond? Brown-headed Cowbirds arrive here in early April and stay through the start of autumn. Look in the skies over the fields and woods around our ponds. They also like to eat at our feeders and on the ground in our yards.

How big are they? The male Brown-headed Cowbird averages eight (8) inches in length. And their wingspan is 14 inches. They weigh in at only around 1 ¾ ounces. The smaller female Brown-headed Cowbird averages 7 ½ inches in length. And their wingspan is 12 inches. They weigh in at less than 1 ½ ounces.

What are their flight patterns? There is nothing distinctive in the flight patterns of Brown-headed Cowbirds during breeding season. However, after breeding season, these birds tend to congregate in large flocks with other blackbirds, including Red-winged Blackbirds. And they will move in swarms from their roosting areas to their feeding areas in the mornings and retrace this path in the late afternoons.

How else do they behave? The Brown-headed Cowbird has a fascinating approach to raising its young – they do not! Females forgo building nests. Instead they put all their energy into producing eggs, sometimes more than several dozen a summer. The female lays one egg in the nest of another bird. Essentially abandoning their young to foster parents, usually at the expense of at least some of the host’s own chicks.

What’s for dinner? Brown-headed Cowbirds feed mostly on seeds from grasses and weeds, with some crop grains. Insects such as grasshoppers and beetles make up about a quarter of a cowbird’s diet, often are caught as cows and horses stir them into movement.

Where do they take up residence? Brown-headed Cowbirds are native to North America and may be found in fields, meadows, and lawns across most of the U.S. It lives in all habitats but is especially often found in forest edges.

When and where do they breed and nest? Brown-headed Cowbirds breed from British Columbia, central Saskatchewan, central Ontario, Quebec, and Newfoundland southward throughout United States except extreme Southeast and Florida. Brown-headed Cowbirds are brood parasites and promiscuous; no pair bond exists. In late spring the female cowbird and several suitors move into the woods. The males sit upright on treetops, uttering sharp whistles, while the female searches for nests in which to lay her eggs. Upon choosing a nest, she removes one egg of the host's clutch, and deposits one of her own in its place.

Where do they migrate? The Brown‐headed Cowbird is a common migrant and summer resident throughout Illinois and a common winter resident in southern Illinois. Spring migrants begin arriving in Illinois in February. They may begin to depart from nesting areas by August or even July.

What is their conservation status? There is low concern. According to the North American Breeding Bird Survey, the Brown-headed Cowbird has seen slight decreases in populations. Partners in Flight estimates the global breeding population at 130 million.

Do they make any interesting sounds? Brown-headed Cowbirds are noisy, making a multitude of clicks, whistles and chatter-like calls in addition to a flowing, gurgling song. Here is a link to the sounds of the Brown-headed Cowbird.

Interesting Facts About the Brown-headed Cowbird:

  • The Brown-headed Cowbird is North America’s most common “brood parasite” - lays her eggs in the nests of other bird species, who then raise the young cowbirds.

  • Male and female Brown-headed Cowbirds are not monogamous and have several different mates within a single season.

  • Brown-headed Cowbird lay eggs in the nests of more than 220 species of birds.

  • In winter, Brown-headed Cowbirds may join huge roosts with several blackbird species - one such mixed roost contained more than five million birds.

  • The oldest recorded Brown-headed Cowbird was approximately 17 years old.

For more information on Brown-headed Cowbirds and sources of information used in this blog (these are the sources that I am using to learn as I blog), please visit All About Birds, the Audubon Society and National Geographic. And the Cornell Lab of Ornithology provides a wonderful source of information for anyone interested in learning more about birds.

The Carillon at Stonegate community is very fortunate to have a variety of wetland, forest and prairie environments conducive to a variety of birds and other wildlife, plants and insects. Our community and the Kane County Forest Preserve do an exceptional job in maintaining this natural environment – both for the benefit of the birds and wildlife and for our residents to enjoy.

 

Take a hike and see what you can find – and identify!