Friday, March 29, 2013

They're Baaaaack!

Friday, March 29, 2013
7 comments
Uggh! One sure and early sign of spring around these parts is the return of the parasitic nest pirate: the brown headed cowbird.

I looked out at the freshly filled bird feeders this morning and there was a male cowbird, all shiny black body and chocolate-brown head. The male cowbirds return first in spring and the females follow a week or so later. Once everyone is back, they begin their traditional business of courting and making whoopee. The male emits (because it can't really be called "singing") a burbling sound that rises in pitch, ending in a piercing squeak. As he vocalizes, he raises his bill to the sky, trying his best to look at once handsome, regal, fierce, and ready for some lady action. In the next week or so, our farm will become a noisy cowbird singles bar.

When the songbird nesting season starts in about a month, the female brown-headed cowbirds will spend their time watching and waiting. They are very clever at finding the nests of other bird species: warblers, thrushes, tanagers, sparrows, vireos, and many others. Once she spots a nest, a female cowbird will inspect it to see if it has eggs in it. If it does, and if she has a fertilized egg ready to go, she may drop it right there in the nest.

Then she simply flies off to look for another male cowbird, another nest of an unsuspecting songbird into which she can deposit an egg. This nest parasitism evolved from the nomadic lifestyle of the cowbird. Cowbirds traditionally followed the large herds of bison as they roamed across the continent, eating the insects the herds kicked up. As the herds moved, so did the cowbirds, a lifestyle which did not leave any time for nest building or young rearing. So the brown-headed cowbird figured out a way to reproduce successfully by having other birds raise their offspring.

My lifer summer tanager was a handsome adult male, sitting on my parents' platform feeder in our small-town backyard. It was feeding a fledgling brown-headed cowbird.

Each spring I have slight urge to do something to help our songbirds avoid being parasitized by cowbirds. And each spring I realize just how futile this would be. We do cut back on ground feeding, especially on offering cracked corn, when the cowbirds are around. Secretly I'd like to ask for a week-long visit from the Fish & Wildlife Service folks who "control" cowbird populations in the Kirtland's warbler's nesting range. They have large, baited cages where cowbirds check in but they don't check out. A cowbird Hotel California.

Alas they are native birds, so, as much as I despise them, I accept them. And sometimes I even sing about them.

7 comments:

On March 29, 2013 at 10:13 AM Rondeau Ric said...

We have had cowbirds all winter which isn't encouraging.
Our feeders are buried in grackles, redwings and yes, cowbirds.
Red-bellied woodpeckers can move them out but the rest of the birds wait for them to leave.

On March 30, 2013 at 5:21 PM xboy said...

Bill

They are truly amazingly adapted birds. Back when they followed the buffalo herds, they could not nest.

On March 31, 2013 at 2:38 PM isaiah43123 said...

I've always thought of these feed hoggers as pests but now appreciate their efforts at survival.

On March 31, 2013 at 8:04 PM Marilyn Kircus said...

One of my favorite volunteer jobs was feeding/watering brown-headed cowbirds that came into a large trap. We kept them throughout the season to attract other cowbirds and released any other birds that got trapped. At the end of the season, they died. This was to help bring back the golden-cheeked warbler and black-capped vireo.

Last spring, the brown-headed blackbirds arrived after the red-winged blackbirds at Malheur NWR in the Oregon High Desert, but ahead of the yellow-headed blackbirds. The yellow-headed blackbirds could drive off the red-wings but the tiny cowbirds stood up to them.

On March 31, 2013 at 10:06 PM Warren and Lisa Strobel said...

Funny, we just had one show up at out house here in Annapolis, Maryland today.

On April 1, 2013 at 12:51 PM Bob said...

I think cowbirds get a bad rap. As you said, they were here long before us and are part of the ecosystem. If our farming practices and feeders have increased their numbers we should modify our own behavior but I think we are not far-sighted enough or wise enough to interfere in other ways. Great blog BTW.

On April 16, 2013 at 12:36 PM polybill said...

bill you would be interfering with natural selection,then maybe your one of those yanks that dont believe in evolution.


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