Most mother birds sit on their eggs to keep them warm so they will hatch, but a mother cowbird never does this. She doesn't even build a nest of her own. Instead she lays one egg in each of four or five different birds' nests. Then she flies off and never comes back. Other birds always egg-sit and baby-sit for her. This is strange, but there is a reason for it.
Before people killed off the buffalo that used to roam on the plains by the million, the cowbird was really the buffalo bird. Its main food was a little wormlike creature that lived under the skin of the buffalo. To get this food the bird naturally had to be where the buffalo were, and the buffalo always kept moving in search of grass.
The mother buffalo bird could not eat her usual food and raise a family at the same time. But by leaving her eggs in the care of a foster mother the buffalo bird gained freedom to look for food, and her babies grew up all right.
When the buffalo disappeared, the birds had a problem. They had to find a new kind of food. This they managed to do, and instead of following buffalo they followed cows. That, of course, is where the name comes from. But cowbirds didn't change their odd egg-laying habits.
The buffalo had itchy skins, and telegraph poles made wonderful scratching posts. The only trouble was that buffalo were such big animals they pushed the poles over. In the old days many a telegram was late because some cowbird had not found a little worm under the skin of some big buffalo.
