Naturalists have ventured that cowbirds
adapted to this nomadic existence by becoming brood parasites and depositing their eggs in nests built and incubated by birds of other species.
In Hawaii, Van Riper (1976) observed a Hawai'i 'Amakihi (Loxops virens) building on top of the nest of an 'Elepaio (Chasiempis sandwichensis), while Mahan (1954) wrote of a Yellow Warbler nest superimposed on that of a Red-eyed Vireo (Vireo olivaceus); the latter instance also involved repeated parasitism of both species by Brown-headed Cowbirds
host suitability is dependent on several factors, including overlapping breeding seasons, acceptance of cowbird
eggs, and nest accessibility to laying female cowbirds
(Sealy et al.
Later researchers dismissed the idea, questioning whether the young cowbirds
could even grasp and yank off the parasites.
Nest parasitism by brown-headed cowbirds
represents a threat to the conservation of some bird species (Smith et al.
Critics have waxed lyrical about the numerous images that have remained with them long after the final credits, such as the footage of brown pelicans, who keep a keen eye on dolphins following schools of anchovies, or cowbirds
steering clear of bison locking horns, or the bald eagles who let grizzly bears do the hard work in catching salmon before swooping down to steal them.
Sealy and Lorenzana (1997) list several observations of fledged brown-headed cowbirds
receiving food from more than one bird species or from a species different from that of the original host.
It also shows how the death of large mammals 20,000 years ago led to the disappearance of one species of cowbird
The disease-causing bacterium Escherichia coli O157:H7 is present, but rare, in some wildlife species of California's agriculturally rich Central Coast region, an area often referred to as the nation's "salad bowl," reports a team of researchers led by a scientist from the University of California, Davis, which found occasional infections in fecal samples of wildlife species common to the area, including cowbirds
, coyotes, crows, mice, and feral pigs.
Experts agree that any reduction in forest management, including the planting of tens of thousands of acres each year and the control of brood parasite cowbirds
, will result in a quick decline of the species.
smuggle eggs into flycatcher nests, where flycatcher chicks have to compete with the hulking, alien offspring.
Meanwhile, the Cowbirds
, who represented the real Communists, were able to take over Mother Stork's nest and replace her eggs with their own:
She describes the loathing she felt when she looked out to see cowbirds
at her bird feeder and thought: "Hey, you parasites, get your beaks off my seed" (p.
are a New World blackbird, which - like cuckoos - lay their eggs in the nests of other birds, though evolution made no attempt to make their eggs look like those of their hosts.
We have encouraged a class that lives by parasitism, the mode of life of organisms that suck another's blood or steal their time and effort, like cowbirds
who destroy the eggs of warblers, then lay their own eggs in the nests, tricking the warblers into rearing the raucous cowbird