West Nile Did Severe Damage to Bird Species

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Many Americans think of dead birds when they think of the West Nile virus. That's because birds such as crows and jays seemed to drop like flies as the virus swept across the country. A new study names the birds that were the hardest hit and finds that some species may never be the same.

MICHELE NORRIS, host:

This is ALL THINGS CONSIDERED from NPR News. I'm Michele Norris.

ANDREA SEABROOK, host:

And I'm Andrea Seabrook.

Eight years ago this spring, a mysterious virus started killing birds in New York City. Scientists soon identified it as the West Nile virus, which came through Europe and the Middle East. Since then, birds and mosquitoes have spread the virus across the country - nearly a thousand people have died after getting West Nile fever. But no one knows how many birds the virus has killed.

NPR's John Nielsen reports that a new study says it had a big impact on some well-known species.

(Soundbite of birds chirping)

JOHN NIELSEN: The trees in Washington's Rock Creek Park are usually thick with noisy birds, but five years ago these woods went weirdly quiet.

Peter Mora, an ornithologist with the Smithsonian Institution says that's when the West Nile virus arrived.

Mr. PETER MORA (Ornithologist, Migratory Bird Center, Smithsonian Institution): There weren't as many crows. There weren't as many robins for a while there. Chickadees seemed to have disappeared and many people were noticing this. My neighbors were noticing this. Where did all the crows gone? The question was: How large a scale the impact was there actually?

NIELSEN: Mora has been trying to gauge that impact ever since. And in a new paper in the journal Nature, he and some colleagues say they now know which bird species were hardest hit. To get these answers, they sorted through a national census of breeding birds that's been done every year since 1966.

Ms. SHANNON LaDEAU (Migratory Bird Center, Smithsonian Institution): Where census and scientists go out in the first week of June and count all the birds they hear.

NIELSEN: Shannon LaDeau is a colleague of Mora at the Smithsonian. She says the team analyzed data for 20 widespread bird species. Seven of them appear to have been hard hit by the virus. For example, nearly half of the American crows in the United States may have died. Other big losers included common backyard birds like the American robin, the blue jay, the chickadee, the house wren and the blue bird.

The study also showed that the virus hit harder in some places than it did in others. Around Washington D.C. for instance, it killed off 90 percent of the crows. Perhaps most intriguingly, according to LaDeau, this study shows that in the places where the virus killed a lot of birds, it also killed a lot of people.

Ms. LaDEAU: The bird impacts and the human impacts moved as a common wave across the continent.

NIELSEN: LaDeau says that wave of West Nile infections has now peaked. The rate of human infections is slowing and some of the bird species like house wrens and blue jays have bounced back. But the outlook for the other five species isn't clear yet.

The authors of this study say it shows that wild birds can be an early warning system for emerging diseases like the West Nile virus. They also say that more of those diseases like the Asian bird flu may be on the way.

John Nielsen, NPR News, Washington.

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