Here's a peek at a "freebie" that will be released during my annual Audubon event towards the end of April. Pictured are the Brown-headed cowbirds. The set will include them as well as the Shiny and the Bronzed cowbirds. Cowbirds are stocky blackbirds with a fascinating approach to raising its young. Females forgo building nests and instead put all their energy into producing eggs, sometimes more than three dozen a summer. These they lay in the nests of other birds, abandoning their young to foster parents, usually at the expense of at least some of the host’s own chicks. The record holder is a female Bronzed Cowbird that laid 17 eggs in a hooded orioles's nest. Some birds, such as the Yellow Warbler, can recognize cowbird eggs but are too small to get the eggs out of their nests. Instead, they build a new nest over the top of the old one and hope cowbirds don’t come back. Some larger species puncture or grab cowbird eggs and throw them out of the nest. But the majority of hosts don’t recognize cowbird eggs at all. The Brown-headed Cowbird is found throughout southern Canada, the entire United States and North and Central Mexico. It is a short distance migrant. Brown-headed Cowbirds move south as far as 530 miles between breeding and wintering grounds.it is found throughout southern Canada, the entire United States and North and Central Mexico. It is a short distance migrant. Brown-headed Cowbirds move south as far as 530 miles between breeding and wintering grounds.