How young cowbirds know they're cowbirds

Juvenile Brown-headed Cowbird photo by Simon Pierre Barrette

I’ve been seeing a lot of cowbirds under the feeders lately. Brown-headed Cowbirds parasitize the nests of other birds. 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.

Adult female and male Brown-headed Cowbird

photo by Lisette Lebaillif

There are 144 different host species documented that raise Brown-headed Cowbird young, so the incubation and parental care of Brown-headed Cowbirds varies greatly depending on the nest in which they are deposited. If they survive, they leave the nest in about 8-13 days but continue to be fed by the host parents for between 18 and 35 days.

You have to wonder, how the cowbirds learn they are cowbirds and find their way back to their flock to mate with their own kind?

Several published studies on the subject have found that it is due to adult cowbirds checking 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.

Juvenile cowbirds, which fledge during the summer months, leave their foster parents about two weeks after hatching to 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.

This theory was reinforced by an experimentwhere cowbirds were housed with canaries during the first winter of their lives. With no further instruction from adult cowbirds, the young cowbirds thought they were canaries by spring. They made sexual advances at other canaries and sung canary songs.

Related Articles:
- How Do Cowbirds Learn to Sing? http://goo.gl/n6kYS 

- Brown-headed Cowbirds http://sheabirdno1.blogspot.com/2009/05/cowbirds.html 

- How Do You Tell a Female Indigo Bunting from a Female Cowbird? http://goo.gl/SpQUX