USGS: Wildlife die-offs no cause for alarm

Some 5,000 red-winged blackbirds dead in Arkansas. More in Louisiana. Fish going belly-up in the Chesapeake.

Amazingly, these things happen all the time, wildlife experts say.  There's been no wildlife apocalypse, nor is there likely to be one soon.

Yesterday, the U.S. Geological Survey issued a press release saying its scientists had concluded, based on preliminary tests, that the bird deaths in Arkansas on New Year's Eve and those in Louisiana were caused by impact trauma.

"Preliminary findings from the USGS National Wildlife Health Center's Arkansas bird analyses suggest that the birds died from impact trauma, and these findings are consistent with the Arkansas Game and Fish Commission's statement," the press release said. "The State concluded that such trauma was probably a result of the birds being startled by loud noises on the night of Dec. 31, arousing them and causing them to fly into objects such as houses or trees. Scientists at the USGS NWHC performed necropsies—the animal version of an autopsy—on the birds and found internal hemorrhaging, while the pesticide tests they conducted were negative. Results from further laboratory tests are expected to be completed in 2-3 weeks."

"Although wildlife die-offs always pose a concern, they are not all that unusual," said Jonathan Sleeman, director of the USGS NWHC in Madison, Wis., which is completing its analyses of the Arkansas and Louisiana birds. "It's important to study and understand what happened in order to determine if we can prevent mortality events from happening again."

In 2010, the USGS NWHC documented eight die-off events of 1,000 or more birds, according to the press release. The causes: starvation, avian cholera, Newcastle disease and parasites, according to Sleeman. Such records show that, while the causes of death may vary, events like the red-winged blackbird die-off in Beebe, Ark., and the smaller one near Baton Rouge, La., are more common than people may realize.

According to USGS NWHC records, there have been 188 mortality events across the country involving 1,000 birds or more during the past 10 years (2000 - 2010). In 2009, individual events included one in which 50,000 birds died from avian botulism in Utah; 20,000 from the same disease in Idaho; and 10,000 bird deaths in Washington from a harmful algal bloom.

The Washington Post wrote a story over the weekend that included a look at millions of fish -- mostly spot, but also some croaker -- dying in the Chesapeake Bay.

Officials' theory there: These fish are particularly vulnerable to cold and were killed when water temperatures dropped suddenly and sharply in late December. Most of the dead were juveniles. "It's colder than it's been in 25 years,"  Dawn Stoltzfus, a spokeswoman for the Maryland Department of the Environment, told the Post. In 1976, 15 million were killed during a cold snap.

The New York Times also took on the subject, exploring why people often suspect a sinister culprit instead of, well, just nature at work.