Parasitic Cowbirds victimized by politically correct foresters
Female black-capped vireo feeds cowbird chicks in her nest. Cowbirds are just one North American species that practices parasitism.

For the cowbird, it is an unfortunate fact of life that human politics, ignorance and arrogance are almost always bedfellows.

That’s because not many humans like cowbirds these days. It has become politically correct to blame the cowbird for an impending avian disaster caused by human destruction of forests everywhere.

Somewhere, someone started bad-mouthing these most unusual of our songbirds, and prejudice against cowbirds has broken light speed getting to the realm of ignorance. For example, I recently heard a state forest biologist say "you ought to shoot all the cowbirds you see."

Bad advice. Number one, killing any migratory songbird is a violation of the U.S. Migratory Bird Act. Number two, the current human disdain for the crafty cowbird is steeped in 1990 politics where only big time welfare recipients like corporate farmers, major corporations and politicians are allowed to feed at the public trough.

How could this tiny, unremarkable-looking bird become the victim of our ever-vacillating climate of political correctness? That’s an easy one—cowbirds are not sugar farmers or industrial polluters, but it is a parasite without a vote.

Cowbirds practice what is known at "brood parasitism" and is an example of an "obligate parasite" because it is locked into victimizing other birds which hatch and then raise its young. It is the cowbird’s only strategy, one it is "obliged" to use.

Cowbirds build no nest of their own and lay their eggs in at least 200 different species’ nests instead. It is a North American variation on the European cuckoo’s behavior—the root word for the word "cuckold."

About 7 inches long, the brown-headed variety, so-named because the male’s head is brown on a black body, is one of two cowbird species in North America. The brown-headed is by far the most widespread, living in nearly every state. The other is the bronzed cowbird, and it enters the U.S. infrequently in the southwestern states. Three other cowbird species reside in South America.

According to the Encyclopedia of North American Birds, the species got its name by associating with cows. In the Great Plains, they were called "buffalo birds" because they hung around herds, picking up insects revealed by bison movements.

Cowbird parasitism involves a lot of scouting. Probably for this reason, cowbirds are among the early arrivals during spring migration. Typically, the female watches a smaller bird build its nest. Then, usually in early morning under dim light, she visits her victim’s nest when the nest-builder is absent. The visit is made after a host bird lay eggs but before it has begun incubating its own eggs.

The female cowbird lays her egg quickly and leaves, returning later to destroy at least one of her host’s eggs by jabbing it with her beak and flying away with it. She is able to distinguish between her own eggs and host eggs.

About half of all host species tolerate the cowbird’s white with brown speckled egg, incubate it and raise the cowbird nestling as if it were its own offspring.

Since cowbird eggs hatch more quickly than most host eggs and smaller birds are the most frequent targets, baby cowbirds are usually much larger than the host’s own babies. When possible, the baby cowbird tosses at least one of the host’s young out of the nest, thus ensuring it will get more food.

Some birds will not tolerate a cowbird egg. The gray catbird and robin, for example, throw out cowbird eggs. Others bury the cowbird egg and their own first egg or eggs by building another nest floor over the eggs. Still other species, such as cardinals and yellow-breasted chats, simply desert parasitized nests. 

Birds most frequently parasitized by cowbirds include all species that nest in open trees, bushes or on the ground. Hole-nesting species like woodpeckers, chickadees and bluebirds are seldom victims.

While cowbirds are the only North American parasitic birds "obliged" to parasitism as a way of life, there are many other species that habitually lay their eggs in other birds’ nests.

Black-billed and yellow-billed cuckoos, grebes, rails, the roadrunner, brown thrasher, starling, sparrows and some finches all victimize other birds. The duck family has several members whose behavior approaches obligate parasitism--21 species are known for this behavior. The redhead and the ruddy duck are well known parasites. Several pheasant species are parasitic, and both California and Bob White quail lay in other ground-nesting birds’ nests.

Cowbirds have become a politically correct target of human prejudice, not only because of their behavior, but also because of massive destruction of forests. With more and more forest-dwelling species left without preferred nesting spots, they nest in open places where they are vulnerable to cowbird parasitism. These migratory forest-dwellers are among those whose numbers are crashing in the Americas, and the cowbird has been labeled as one reason by some biologists—a claim championed by some foresters.

It is at least ironic that foresters, those "trees are crops" guys who love clear-cutting and pine plantations, have found a 7-inch bird to blame for part of the destruction they promote.

If there is a political lesson in the cowbird’s story, it is in the details of how any species becomes a parasite. One favored theory among biologists is that parasitic birds developed their behavior after they lost or while they were losing the typical avian drive to defend a territory.

Applied to humans, we label as parasites those who have no territory, no property, to defend. In the case of the poor, the avian parasite example suggests humans might be less parasitic if they had their own property to defend.

In the case of big corporations, their humans are so distant from the land that they have abandoned defending it and now concentrate on raping it instead. Taking their territory away or requiring them to live amidst their own filth and destruction might remove the worst welfare abusers from America’s roll of parasites instead of the lonely cowbird, the latest victim in the continuing legacy of Reaganism and 1990s political incorrectness.

12/2/97

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