The Brown-Headed Cowbird is common throughout North America. The male brown-headed cowbird is glossy black with a contrasting dark brown head, while the females are dull grayish brown. A female cowbird can have several mates but instead of nesting, will lay her eggs in the nests of other bird species which foster the babies.
Studies have shown that the cowbirds don’t just drop an egg and move on. The females occasionally check in on the little bundles they’ve left behind. If the egg has been removed by the bird family, the female cowbird may go in and destroy the whole nest which results in the start of another batch of eggs being laid. The cowbird can then try to slip another egg into the nest.
Brown-headed Cowbird females lay around 35 eggs in a season. They have been documented to drop eggs in the nests of at least 220 host species, including hummingbirds and raptors. Sometimes the young cowbird is fed by the host parents at the expense of their own young. Sometimes the cowbird can't survive in families that don't eat bugs like the vegetarian finches.
If the foster family is successful in raising the cowbird, they will start out with the basic baby call of “feed me, feed me”, but they inherit a basic unstructured song. Once they are old enough to forage on their own they join up with other cowbirds and complete their final songs.
Most birds raised in captivity that never hear the songs of their parents learn a different song with some inherited components. For more information National Wildlife Federation has a complete article on bird song and Nova Science Now has a short video on how birds learn to speak.