The Cowbird by John Burroughs — Read

The cow blackbird is a noticeable songster in April, though it takes a back seat a little later. It utters a peculiarly liquid April sound. Indeed, one would think its crop was full of water, its notes so bubble up and regurgitate, and are delivered with such an apparent stomachic contraction. This bird is the only feathered polygamist we have. The females are greatly in excess of the males, and the latter are usually attended by three or four of the former. As soon as the other birds begin to build, they are on the _qui vive_, prowling about like gypsies, not to steal the young of others, but to steal their eggs into other birds' nests, and so shirk the labor and responsibility of hatching and rearing their own young.

The cowbird's tactics are probably to watch the movements of the parent bird. She may often be seen searching anxiously through the trees or bushes for a suitable nest, yet she may still oftener be seen perched upon some good point of observation watching the birds as they come and go about her. There is no doubt that, in many cases, the cowbird makes room for her own illegitimate egg in the nest by removing one of the bird's own. I found a sparrow's nest with two sparrow's eggs and one cowbird's egg, and another egg lying a foot or so below it on the ground. I replaced the ejected egg, and the next day found it again removed, and another cowbird's egg in its place. I put it back the second time, when it was again ejected, or destroyed, for I failed to find it anywhere. Very alert and sensitive birds, like the warblers, often bury the strange egg beneath a second nest built on top of the old. A lady living in the suburbs of an Eastern city heard cries of distress one morning from a pair of house wrens that had a nest in a honeysuckle on her front porch. On looking out of the window, she beheld this little comedy, -- comedy from her point of view, but no doubt grim tragedy from the point of view of the wrens: a cowbird with a wren's egg in its beak running rapidly along the walk, with the outraged wrens forming a procession behind it, screaming, scolding, and gesticulating as only these voluble little birds can. The cowbird had probably been surprised in the act of violating the nest, and the wrens were giving her a piece of their minds.