Bird are dying - fell from the top

Birds are dropping in droves. The thing is, it's perfectly normal.
In recent days, 5,000 blackbirds dropped dead in Arkansas. Dozens of jackdaws in Sweden fell from the sky as well. So did a few hundred turtle doves in Italy.

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Associated Press

Hundreds of dead birds cover the Morganza Highway in Pointe Coupee Parish, La., on Monday.

The natural questions: Are these deaths somehow linked by a common cause, a sign of an impending apocalypse or the result of a common environmental trigger? Biologists say it's unlikely.
"Large mortality events in wildlife aren't that uncommon," says Paul Slota, spokesman for the U.S. Geological Survey's National Wildlife Health Center in Madison, Wis., which has been tracking mass animal deaths since the 1970s. "In the last 10 years we have logged 188 cases just involving birds with mortality exceeding 1,000 animals per event."
The causes vary. Some animals starve. Others eat toxic food or get poisoned by people. Many die in severe weather, or succumb to pollution or bacterial and viral illnesses. In many causes, though, the cause remains a mystery.

 For example, one prevailing theory holds that the blackbirds in Arkansas were startled out of their roost by fireworks set off on New Year's Eve, which disoriented them and caused them to slam into buildings, trees and the ground. But some scientists say fireworks aren't the likely cause; if so similar bird deaths would be reported every New Year's Eve, but they aren't.

More

• Louisiana Experiences Mass Bird Kill (01/04/2011)
• Mystery of the Dead Blackbirds Continues (01/04/2011)
• Loud Noise Likely Caused Birds' Deaths (01/03/2011)

On average, between 160 and 200 such "mass death" events in wildlife are reported to the federal government each year, according to the USGS.
The Associated Press also noted that there have been much larger die-offs than the thousands of blackbirds in Arkansas; twice in the summer of 1996, more than 100,000 ducks died of botulism in Canada.
So why the sudden surge in public interest, plus the accompanying fear in some quarters that something sinister might be afoot?
"There's much greater exchange of information nowadays" thanks to the Internet, says Mr. Slota. "The more such events get reported, the more people take interest" and see links that aren't necessarilythere.
Some wildlife declines are truly worrisome but aren't as attention-getting, says Mr. Slota.
For example, in the past three years or so, more than one million bats in the U.S. have died from a fungal affliction called white nose syndrome.
The bats are important pollinators for several plant species, and "the mortality is astoundingly greater" than the blackbirds, says Mr. Slota. But public interest is meager.

Write to Gautam Naik at gautam.naik@wsj.com
Source : wsj.com - January 8, 2011.