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Roy Lukes: The Unwelcomed Cowbird

There is a bird that has been wintering in the South that will very likely be visiting your feeders before the end of the month. You can bet your bottom dollar that not many people will be rolling out the red carpet to welcome back the brown-headed cowbird. However, like them or not, they are here to stay, much like the red-winged blackbirds, common grackles and European starlings.

The mousy gray color, lack of wing-bars and other distinctive markings of the female frequently confuse some of us birdwatchers in spring, having not seen these migrants for many months. It takes a while to get used to these nondescript creatures. During the first year we were married I came home from school one spring day and Charlotte was excited over an unusual bird she had observed on the feeder but couldn’t find it in the field guide.

She was sure it was a very new discovery until, according to her detailed written description, I had to tell her it was a female brown-headed cowbird. At least it was the first one she had seen.

I’ve heard people refer to them as shiftless tramps that neither hatch their own eggs nor care for their young. It is quite normal to despise the parasitic habits of these “brownheads.” Their scientific name, Molothrys ater, (mo-LOTH-ris AYE-ter) refers to a dark, greedy beggar. However, in taking a closer look at this carefree “villain” perhaps you will develop a slightly more tolerant outlook toward this generally disliked bird.

A female cowbird is very plain and rather drab. Photo by Roy Lukes.

A female cowbird is very plain and rather drab. Photo by Roy Lukes.

I saw my first large flocks of cowbirds at the start of my serious birdwatching while in the army at Fort Sill, Oklahoma. Some large herds of buffalo inhabited the wide-open prairies of the nearby Wichita Mountains Wildlife Refuge, and I would often observe hundreds of these brown-headed beggars following the herds. The buffalo, as they ambled through the grass, disturbed insects into movement which were then caught and eaten by the cowbirds (buffalobirds). The birds also frequently rode upon the backs of the buffalos, presumably consuming insects there, too.

Later during my studies I began to wonder whether the buffalo and cattle-following habits of these birds induced them to lay their eggs in other birds’ nests. Could it be possible that these wide-ranging beasts were continually attracting the female cowbirds away from their nest sites and thereby forcing them to lay their eggs elsewhere, more especially in other birds’ nests? Unfortunately there are few facts supporting such an idea, so this suggestion remains little more than an educated guess.

These monogamous birds do set up a rather well-defined territory in late spring. The earlier-arriving black-bodied, iridescent, brown-headed male, having established his summer quarters, goes into quite a wheezy frenzy when the drab brown females arrive.

They proceed to search for weed seeds, corn, grain and insects as other birds prepare for nesting. Then begins the “dastardly, villainous act” detested by so many people. The female, often appearing to be sly and stealthy in her movements, will locate another bird’s nest and usually will lay a single egg in it – white with tiny brown spots.

Studies indicate that a female cowbird will lay from 10 to 12 eggs during the nesting season. Interestingly their eggs have a slightly shorter incubation period than those of their victims, such as a red-eyed vireo, ovenbird, American redstart, yellow warbler, chipping sparrow, song sparrow and other warblers and flycatchers.

It is funny, as well as a bit sad, to see a tiny chipping sparrow feeding a fledgling cowbird about twice her size. The nests of at least 200 or more species of birds are known to be parasitized by the cowbird. The burning question that repeatedly comes to my mind is, “Could it be possible that the majority of the victimized nests are those of ‘newly-wed’ birds?” Maybe these birds have a lot to learn about building well-concealed nests and flying through the woods so as not to lead the female cowbird to their locations. Let’s face it. Bird nest predation has been around for eons.

Perhaps one could look at this form of brood parasitism as a type of conditioning leading toward more alert birds and better nest-builders. Fortunately there are few alarming consequences related to the egg-laying tactics of the cowbird. One involves the rare Kirtland’s warbler of Lower Michigan (now nesting in a few areas of Wisconsin) where a vigorous program to control the number of cowbirds seems to be helping the warbler succeed.

I don’t envy those people who have been, or are actively involved, in the decision-making process of choosing which species of birds will be removed from the protected list. The species not protected by the Migratory Bird Species Act are the European starling, house sparrow, Eurasian collared dove and the European goldfinch. All others are protected.

A cowbird egg is heavily speckled with brown. Photo by Roy Lukes.

A cowbird egg is heavily speckled with brown. Photo by Roy Lukes.

To what degree can we “tailor-make” our state, or our own property for that matter, by deciding which birds, mammals or plants may stay and which ones must go? Believe me there are more ways than one whereby this can be accomplished. For example, construct a new 50-mile-long, four-lane highway having a right-of-way that is 600 feet wide and a lot of plants, birds and mammals will be gone. That’s what I call tailor-making the environment on a very large scale.

Ideally one should study all the available facts before completely condemning a particular bird species, such as the brown-headed cowbird. Obviously they do us a tremendous favor by eating great numbers of injurious insects. We are forced to admit that these feathered vagabonds are neither bad nor good. In fact, as we carefully examine the total web of animal life, each species in its own niche, we would be surprised that, by our own standards, many birds are not as good as we think they are. And yet, each species appears to be of special value to its environment in some way.

Incidentally, where do you think you would fit in the big web of life that involves all creatures? How long would your “good deeds” and “bad deeds” list be?

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