The Cowbird

By Al Lowe
Contributor

We have quite a few birds which are black, or mostly black, in Northern Ontario. This is one of which is quite different from all the others in many ways. That is the Cowbird, or officially the Brown-headed Cowbird (Molothrus ater).
Now this bird does not even look the same as the rest of the blackbirds. It is smaller, and it has a sturdy beak, something like that of a sparrow or a finch. The male is a dark glossy black, except for his head and neck, which are quite dark brown. The females and young birds are very dull and nondescript brownish grey.
How about that name - Cowbird? Well, these birds have a habit of hanging around cattle, horses and other big animals. They ride on the backs of cows, picking up all the flies they can find. And they also walk all around where cattle are grazing, catching insects stirred up by the big animals’ feet. They spend much of their time doing this.
They have lots of time because they do not raise their own young. The Cowbird is the only bird parasite in North America. In the spring at egg laying time, the female cowbird skulks around until she finds the nest of a smaller bird, a warbler or sparrow, for instance. When the real mother is away, she slips in and lays and egg in the nest.
Birds react in different ways to the presence of this egg, which is always larger than its own. Some will work at it until they push it out. Some will build a second nest over the top of the first one. And some will just abandon the nest and build another one. But most just merely accept fate and go ahead philosophically incubating the eggs.
When the young hatch, they young cowbird is bigger than his nestmates. This means that, at feeding time, his beak is up higher than the others. So he gets most of the food or maybe all of it. The other young ones starve. Or the Cowbird may push the other ones out of the nest altogether. Whatever happens, the result is always the same. The young Cowbird survives and the others do not.
When he is big enough to fly and look after himself, he simply goes off to join a flock of Cowbirds, leaving his foster parents with nothing at all to show for their work.
Actually, in some ways, the Cowbird is quite beneficial. The insects it eats are almost all harmful, and its major diet is insects. However, in the balance, it does destroy a great many warblers and sparrows, whose consumption of insects and noxious weeds would be enormous.
In the fall, the Cowbirds flock with all the other blackbirds, in their thousands in the north, and millions in the south. The Brown-headed Cowbird has a lifestyle which is unique and not very admirable.