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Why cowbirds have a bad rep



Hi Carolinabirders,

Great Crested Flycatcher joined the suburban migration crowd on Ninth
Street today. Not a new yard bird though, had one last year around this
time.

On Tue, 30 Apr 2002 jwbloor@duke.edu wrote:
>
> Finally, I find it very curious that Brown-headed Cowbirds have
> such a bad reputation here, when in England the parasitic Cuckoo
> is beloved as the harbinger of spring.

I would guess that at least some of this comes from the un-natural-ness of
cowbirds through most of their US range. Correct me if I'm wrong, but
Cuckoos are native throughout England. Cowbirds, meanwhile, are naturally
foreign to the eastern US, originally dwelling on the Great Plains amid
herds of Bison and prairie dog towns. They require very short grass or
bare ground for foraging, and so followed grazing animals around.

However, the clear-cutting of the eastern forests, and conversion of much
of them to farms and ranches, opened a way east for the cowbirds. The age
of the lawnmower and proliferation of lawns (often including bird
feeders), golf courses, powerline cuts, and mowed roadsides and highway
partitions has only increased the feeding bonanza, while fragmentation of
the forests gives them ever more breeding opportunities. Not only did the
Brown-headed Cowbird spread west from the Great Plains, but the Bronzed
has to a lesser extent spread from the southwestern deserts, and the Shiny
up from the Caribbean.

Breeding birds in the grasslands and edges had lived with Brown-headed
Cowbirds for so long that they often could recognize and abandon
parasitized nests and start over, but forest interior species with only a
few decades' experience with brood parasites have proven defenseless so
far. And species which have become endangered primarily because of fire
suppression and habitat destruction, like Kirtland's and Golden-cheeked
Warblers and Black-capped Vireos, are being pushed ever closer to
extinction by cowbird parasitism.

So why are cowbirds so unpopular in the US? Maybe because they keep
reminding us how badly we've screwed up this country's wildlife habitat!
Want to do something about it? The best defense is large unfragmented
blocks of habitat. Keep large forest tracts intact. Try to promote new
forest habitat along the edges of existing tracts. Convince people to stop
mowing everywhere, so the grass gets long and cowbirds stop feeding there.
And push for new roads, golf courses, playgrounds, housing developments,
and other lawnmower-intensive areas to be clumped together, as far from
forest as possible.

Good birding,

Josh


Joshua S. Rose
Duke University
Department of Biology (Zoology, R.I.P.)

jsr6@duke.edu
http://www.duke.edu/~jsr6/