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WHY IS THERE A BIRD NAMED AFTER A COW? (People, beef, climate change and grassland birds)

By Nic.Korte

In my last blog, I discussed how grasslands have changed drastically in the past century and a half. I mentioned the many birds whose populations have suffered enormous declines as a result. But, as always, “it is an ill wind that does nobody good.” Winners in this change of landscape are cowbirds—our local variety is called the brown-headed cowbird.

Now is a good time to discuss cowbirds because we will soon be seeing large flocks of birds—often dismissed as simply “blackbirds.” Although uncommon here in winter, flocks we will be seeing may contain thousands of cowbirds. The breeding population, confined to the US and parts of Mexico and Canada, is estimated at 120 million birds (http://www.allaboutbirds.org/guide/Brown-headed_Cowbird/lifehistory). 

(male brown-headed cowvbird by Jackson Trappett)

In the old, old days, this species was mostly restricted to the prairie and followed the buffalo. Their feeding habits involve eating whatever insects large animals kick up as they graze. They will also land on the animals and pick off whatever insects inhabit their coats. I recently saw a couple of cowbirds perched on some horses in a field near Collbran. 

Buffalo were nomadic. How could a bird that lays eggs in a nest raise young and follow wandering buffalo herds? Nesting seasons are too long. Cowbirds solved the problem by evolving into brood parasites. They don’t build a nest. They don’t rear their young. They lay their eggs in the nests of other birds. Typically, cowbirds hatch first and completely out-compete and kill their typically smaller nest-mates. 

The buffalo are gone, but cows make an excellent replacement. Any large livestock will do, and so will feedlots. Now that expansive forests are gone; large livestock and cowbirds are everywhere. Many species that did not evolve with cowbird resistance are in such serious trouble that cowbird control (trapping and shooting) has been necessary to stave-off extinction (http://www.tpwd.state.tx.us/publications/pwdpubs/media/pwd_bk_w7000_1148.pdf).

An example of an endangered species thought to be especially vulnerable to cowbird parasitism is the black-capped vireo. Black-capped vireos are neotropical migrants that nest in the US and winter in Mexico.  This bird was mist-netted in January in the Mexican highlands (http://www.gjsentinel.com/blogs/birds_and_more/entry/mexican-haiku).

(black-capped vireo, mist-netted in Jalisco, Mexico-January 2014)

Unfortunately, the raising and feeding of cattle brings more to this story than the creation of habitat for brown-headed cowbirds. It might surprise you to learn that many scientists believe if you want to reduce your personal greenhouse gas emissions, the best thing is to stop eating beef—the combined fossil fuel input for beef production may be the single biggest contributor to carbon dioxide in the atmosphere and the greenhouse effect (http://www.worldwatch.org/system/files/Care2%20041812.pdf).

The reason for the high fossil fuel input is that most beef cattle aren’t grazed. They are fed feed derived from grains--grown on dwindling grasslands. That means farm machinery emissions, fertilizer use and production, emissions from cattle themselves, and soil erosion—all contributors to climate change. Marginal grasslands, that is, those that are too rocky for a plow or where irrigation isn't feasible, well, they can be used for direct grazing (perfect for cowbirds) and much of this land has been overgrazed (http://www.blm.gov/wo/st/en/prog/grazing.html).

I hate for this to sound so dire, so let’s not be pessimistic. I suggest there's another approach. It seems to me that having wildlife to view and having nice habitat for hunting, hiking, bike-riding etc. transcend politics and economics. We as a species, need to practice some restraint (See the previous blog to this one.). Cowbird over-population, declineof grassland birds, human consumption of beef, and climate change are intertwined. We can restrain ourselves. We don't have to eat beef every day or maybe every week. That will help!

This post provided by Nic Korte, Grand Valley Audubon Society. Send questions/comments to audubongv@gmail.com. [To learn more and to participate in the activities of Grand Valley Audubon, please see our website at audubongv.org and “like” us on Facebook!]
 

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