About us: We own the Wild Birds Unlimited nature shop in East Lansing, Michigan,
a store that provides a wide variety of supplies to help you enjoy the birdwatching hobby.

This blog was created to answer frequently asked questions & to share nature stories and photographs.
To contribute, email me at bloubird@gmail.com.

Monday, April 25, 2016

Brown-headed Cowbirds scout for nests

Adult female and male Brown-headed Cowbird

I saw a male and female cowbird scouting my yard yesterday. Brown-headed Cowbirds parasitize the nests of other birds. It looked like the ones I spotted had their eyes on a cardinal couple. The female Cowbirds wander about, laying up to 40 eggs per season (April to June) in as many nests of different bird species as they can find. They lay one egg per nest, each day for about 7 days, then rest for several days before another egg-laying sequence.

Human development of the land has caused fragmentation of forest habitat and resulted in a great increase in the edge habitats favored by Brown-headed Cowbirds, and a reduction of forest-interior habitats where they don’t like to venture. As a result, a number of forest birds' nests are now being used by Brown-headed Cowbirds at an increased rate.

There are 144 different host species documented that raise Brown-headed Cowbird young. Several published studies on the subject have found adult cowbirds check in with young cowbirds while the youngsters are still living with other species. The adult cowbirds help teach fledglings cowbird-specific behaviors before they leave their foster homes.
Eastern Phoebe nest with 5 phoebe eggs & 1 Brown-headed Cowbird egg via Wikimedia Commons
In late summer cowbirds flock together with other cowbirds. Chatter calls, as well as other visual cues help with recognition of their own species. The theory is that cowbirds and other parasitic birds possess a simple behavioral trait or cue that is species specific and helps them recognize themselves as cowbirds. 
Related Articles:
- How Do Cowbirds Learn to Sing? http://goo.gl/n6kYS 
- How Do You Tell a Female Indigo Bunting from a Female Cowbird? http://goo.gl/SpQUX

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