Cowbird Nestmates - Science Updates - Science NetLinks
The relationship between the Brown- headed Cowbird nest in dark cavities, which may make cowbird eggs Tips on wings and other things. A brown-headed cowbird chick is the first to hatch in this eastern phoebe nest. cowbirds are a parasitic species, meaning they lay their eggs in other birds'. Even though Brown-headed Cowbirds are native to North Cowbirds often flock with other species of blackbirds, and they may.
Those species which accept cowbird eggs either do not notice the new eggs, or as new evidence suggests, accept them as a defense against total nest destruction.
A second look at cowbirds and buffalo - btcmu.info
Use feeders that are made for smaller birds, such as tube feeders that have short perches, smaller ports, and no catch basin on the bottom. Avoid platform trays, and do not spread food on the ground. Cowbirds prefer sunflower seeds, cracked corn, and millet; offer nyjer seeds, suet, nectar, whole peanuts, or safflower seeds instead.
Clean up seed spills on the ground below feeders. First, look for any eggs that appear different or out of place. Cowbird eggs are sometimes, but not always, larger than those of the host bird. This is especially true of warblers and small birds, but cowbird eggs are the same size as Northern Cardinal eggs. Cowbird eggs are white to grayish-white with brown or gray spots or streaks.
Look for intact eggs on the ground under active nests. Female cowbirds often evict one or more of the host eggs before they lay their own. However, she may eat the egg instead or damage it and leave it in the nest. Most songbird chicks have a yellow or pale gape.
Cowbird young develop in about days, so they may fledge before you expect the host species to have fledged. That's because mom and dad bring more food to a bigger brood.
And because cowbirds are usually older and bigger than their nestmates, they can easily hog the extra resources.
General Bird & Nest Info
And so the nestmates often starve, or get trampled by the larger, more aggressive parasitic chick. He says understanding cowbird behavior is important because they're spreading further across America, and targeting new species as hosts.
Making Sense of the Research There are about ninety species of parasitic birds birds that lay their eggs in other birds' nestsbut the North American cowbird and the European cuckoo are probably the best known. Of the two, cuckoos are far more ruthless: It's brutal, but it works. Given the cuckoo's strategy, it's surprising that the cowbird doesn't do the same thing. A casual observer would see cowbirds squawking and begging for food with a nest full of birds from another species.
Why not use a winner-take-all strategy like the cuckoo? As you heard in the report, the cowbird actually does have a strategy, but it's best described as winner-take-most. The researchers studied the cowbirds' success by planting cowbird eggs in the nests of a songbird called the Eastern phoebe. The cowbird eggs either were placed alone in the phoebe nests or with two phoebe eggs.
Previous studies have shown that cowbirds seem to prefer two nestmates to more or fewer.Brood parasitism: Cowbird eggs damage host eggs during laying from elevated positions
The fact that the cowbirds in Hauber's study grew faster and ate more when they had nestmates confirms this evolutionary strategy. A cowbird with two nestmates can gobble up the lion's share of the food by outmaneuvering and out-begging its adopted siblings. More siblings makes the competition tougher; fewer siblings means there's less food to be had. Of course, cowbirds with too many siblings sometimes level the playing field by starving out the weakest chicks, but this isn't as deliberate as the cuckoo's killing spree.
Some species of North American songbirds have lived with cowbirds for centuries, and have reached a kind of equilibrium with them. But lately, cowbirds have been branching out into new areas, in large part because of deforestation cowbirds prefer flat, open grassland.