Why I Don't Like Cowbirds

It is the Sunday of Labor Day weekend and I am far from laboring. There is a large spider on one of the poles holding netting in front of the hummingbird feeder, taking in some sun. The squirrels don't seem as active in the trees. As usual, people are not rushing around in their cars or with their lawn mowers. There is the faintest tinge of red in the leaves of the dogwood, another signal that summer is ending, the days are getting shorter and soon I'll be closing up the garden and taking in plants for winter.

Male cowbird, Cape May, NJ (RE Berg-Andersson)

Birds should've ended their breeding and raising of young by now. Many birds are on the move southward, taking advantage of those recent cooler days when the wind comes from the north to give them a push along.

However, amid this sluggishness I hear a high-pitched chatter I recognize. Then I see them, the male cardinal flying across the yard with a begging, scolding, badgering cowbird chick close behind.

It has been some time since I've seen this. Cowbirds are a peculiar species, at least to me. The only way the species can continue is the female - a drag brown, easily overlooked or confused with something else - drops one of her eggs into another bird's nest. The egg hatches, usually ahead of the bird's own eggs, and the chick is usually bigger too. To make sure it gets fed, it can push the other eggs out of the nest, monopolizing the parents. This is what the cowbird chick in my yard was doing with the adult cardinal pair.

And yet, somehow when the chick grows to maturity it knows it is not a cardinal, a robin, a Carolina wren. It flies off and joins with other cowbirds in large flocks, frequently joining with even larger flocks of grackles, redwinged blackbirds and starlings in winter as a way of finding food and protection.

When the adults pair, they are not monogamous and the female can lay eggs from a number of mates in the nests of more than 220 species of birds, according to the Cornell Lab of Ornithology. (Yellow warblers have been known to recognize cowbird eggs and build a new nest and lay a new clutch of eggs over the old. Other birds toss the cowbird eggs out. Cowbird eggs placed in goldfinch nests don't survive because goldfinches eat only seed rather than the insects a cowbird needs.)

Male cowbird flock, Cape May, NJ (RE Berg-Andersson)

Some people find the male cowbird handsome but I do not. These birds were once found solely on farms, following cattle (hence their name). However, according to the bird people at Cornell, once the open grasslands became towns and suburban developments, the birds spread. Now you are as likely to see them at your feeders. I try to chase them off mine whenever possible.

I pity the cardinal. This species seems particularly vulnerable to the parasitizing of its nests. It does not see a cowbird when the bird begs to be fed, it sees young and must feed it. The adult bird is programmed to do that. It does not "see" that this is not a cardinal. In fact, both parents are "blind" to that fact. All they know is the bird must be raised to fledge and then fed until it can take care of itself so it can mate and continue the species next year.

Luckily, cardinals, unlike several other types of birds whose numbers are down because of the cowbird as well as habitat destruction, are far from endangered. They will have several broods a year. There are many cardinals. They will come to my feeder and I will keep it filled for them. 

Unfortunately, cowbirds aren't endangered either. For now, I will have to put up with hearing the continual, annoying, badgering, high-pitched begging whine until something in the cowbird's mind tells it it's time to go find more of its own kind.

Love is Blind

I do not like cowbirds.

They are ugly birds. The male is black with a brown head that looks all black in dim light. The female looks like an oversized, gray house sparrow.

I do not like the female because she also has an ugly habit of dropping eggs in the nests of other birds. This is known as parasitizing.

The cowbird isn't the only bird to do this. Some cuckoos drop eggs into the nests of other cuckoos, for instance.

But parasitizing is the only way the cowbird can continue the species. Cowbirds don't build nests. Nor do they kick out other birds to take the nests, as owls do. It is not known why they must use the nests of songbirds.

That is why at this time of year, when I am hearing the first broods of chipping sparrows, starlings, robins and titmice making a ruckus as they chase their parents begging to be fed, I expect my annual sighting of some pair of adult birds being harried by a particularly large, aggressively hungry chick.

One year I was walking to the train and saw a pair of carolina wrens feverishly trying to fill the mouth of a cowbird chick that was double their size. Cardinal nests are also prone to parasitization and, like the sun rising in the east, I will soon hear the very loud screeching of the cowbird chick in my bushes following an adult cardinal that is desperately looking for something to feed it.

You would think the wren, for instance, would recognize the intruder in its midst. Some types of bird do. The yellow warbler will build an entirely new nest over an existing nest if it spies the larger cowbird egg, neglecting its own eggs in the process of starting over.

But most birds, like the carolina wren and the cardinal, are not programmed that way. If there is an egg, the adult sits on it. And if that slightly larger egg hatches first, as cowbird eggs do, and the chick manages to push some or all of the other eggs or hatchlings out of the nest in order to hog the food, it isn't noticed by the parents. In their minds, they are raising the next generation.

But it's the wrong generation.

In Michigan, where the population of Bachman's warbler was practically wiped out thanks to a nasty combination of habitat destruction and parasitization, it is policy to catch and kill cowbirds within the designated Bachman warbler jack-pine habitat.

It may seem cruel but that has helped the Bachman's population slowly re-grow.

This isn't a problem for the cowbird. This is one bird where the destruction of its usual habitat has helped it.

Cowbirds were farm birds, picking bugs off the cows and the fields. But with "progress" has come suburban developments built on farm fields. There may be fewer farms but the cowbirds adapted and thrived. Too well, in fact.

One thing that amazes me is that after being raised by a pair of cardinals, for example, the cowbird chick will grow up and somehow intuitively know it is not a cardinal. Then it will find other cowbirds and at the correct, programmed time mate and start the parasitation process all over again.

To me this makes the cowbird, literally and figuratively, the dark side of nature.