Nest parasitic cowbirds fatally deceive other species | New
However, many species of birds laid eggs this spring, there is one less species that actually built nests and hatched eggs in them.
Meet the brown-headed cowbird, a parasitic nester and a true slacker and dodger of responsibility in the avian world.
The cowbird is classified as a songbird and enjoys the same protections as other songbirds, but it might not deserve the consideration given to other species. In winter mode, he can hang out with unprotected exotic European blackbirds and starlings, but cowbirds lack the work ethic and self-sufficiency of either.
You might know half of them when you see them. Males and females look like two separate species.
A male cowbird is about 8 inches long with a wingspan over a foot. Its body is black with purplish highlights like other blackbirds, but its head is brown. When they come together with matching blackbirds, they tend to blend in perfectly.
The female cowbird is a bit smaller, 7 inches or a little more in length and with a wingspan usually just under 12 inches. Unlike its male counterpart, the female cowbird is a streaky brownish-grey, somewhat darker on the back and wings than on the belly. She doesn’t look like a cowherd, at least as we understand her.
Cowbirds are regular residents throughout North America. They really are more common today than in pre-colonial times because they thrive better in grasslands and agricultural areas than in forest areas. Forests that were less hospitable to them, of course, in many cases are now cleared or fragmented thanks to us.
Brown-headed cowbirds were once in their prime element on the western plains of North America when they could keep up with the massive herds of bison in the spring and summer. They had a symbiosis with the buffaloes, hanging out with the big, shaggy creatures, catching and eating the insects they excited as they grazed on the grasslands.
When the buffalo herds died out, again thanks to us, cowherds over time adapted to grazing cattle as insect hunters. The birds became so associated with feeding around domestic cattle that their common name became cowbirds. (I was never able to determine their name, if any, before they created an association with cows.)
Cowbirds eat grass and weed seeds as well as grains, as well as various small insects. Insects form an important part of the diet in warm weather, while cowbirds rely much more on seeds during the winter when they are herded together and feed on a mix of blackbirds.
They are not particularly harsh on agricultural crops and are not otherwise destructive of human property or effort. But they are destructive to other birds, including some species that are in decline and don’t need a stab in the back.
As stated above, cowbirds are parasites in the sense that they do not build their own nests. They lay eggs in the nests of other species, tricking these parent birds into raising the cowbird hatchlings.
A female cowbird is not monogamous, mating with multiple males and producing eggs prolifically. She can lay eggs at a rate of nearly one a day for weeks at a time. A single female brown-headed cowbird can lay 40 or more eggs in a spring-summer season.
But the eggs go to the nest of another type of bird. Science documents that cowbirds sneak their eggs into approximately 140 species of other birds’ nests and successfully coax unwitting host birds into raising the resulting cowbird hatchlings.
Cowbirds tend to choose nests of species smaller than themselves. A female often sneaks into a nest and expels one or more eggs from the host birds. She replaces the eggs with her own, perhaps two or three successive days.
Some eggs belonging to it are destroyed by the laying cowbird. Those left to share space with cowbird eggs have a dismal outlook.
Cowbirds hatch earlier and grow faster than other species. Invader eggs produce aggressive young that out-compete hatchlings belonging to them if the appropriate eggs are not destroyed sooner by baby cowherds. And that happens when the host parent(s) break their beaks working to feed the cowbirds’ voracious chicks at the expense of their own.
In sum, cowbird-parasitized nests almost never produce any of the young birds of the species that build, nest, hatch, and care for the hatchlings there.
During this time, adult cowbirds do not share any of the duties of building nests, incubating eggs, or feeding and caring for hatchlings. They shrug off all of these problems and go their own way, which includes parasitizing other nests and, essentially, killing more songbirds of other species to deceitfully propagate their own.
Yes, brown-headed cowbirds are songbirds and are protected as such. But their ways of parasitizing broods have negative impacts on the reproduction of many other species. Some of these species that cowbirds feed on include birds that are threatened or flirting with the endangered species list.
Due to their destructive and destructive lifestyle, many songbird enthusiasts consider brown-headed cowbirds to be a nuisance species.
Maybe cowherds are just going the way of nature, but I don’t respect them.