Saturday, January 8, 2011

Nature Guide: Mysterious Mass Bird Deaths

Thousands of blackbirds fell out of the sky on New Year’s Eve in Beebe, Arkansas, a town about 35 miles northeast of Little Rock. This was followed by strange animal deaths in several different parts of the world. Our Nature Guide Jon Latimer takes a look at these perplexing events.

"First reports of mass die-offs appeared when about 5,000 dead birds were discovered in Beebe, Arkansas, on New Year’s Day. A few days later 500 birds were found dead in Louisiana and several hundred more in western Kentucky. Many of the dead birds were red-winged blackbirds, but there were also grackles, starlings and even robins.

"These events were followed by the discovery of dead jackdaws (similar to our American crow) in Falköping, Sweden, and turtle doves in Faenza, Italy. Then an estimated two million fish were discovered dead in Chesapeake Bay and other fish kills were reported in Brazil, New Zealand and Arkansas. Some 40,000 crabs washed up on English beaches. All these mass die-offs began to look like an international catastrophe.

"In fact mass die-offs are not that uncommon, but they are rarely related. More than 150 are recorded each year by the US Geological Survey. But these events normally go unnoticed by the public because they happen at sea or in rural areas. Since they don’t get reported (although they do appear in popular fiction), people don’t try to link them together into a larger pattern. The die-offs of birds in Arkansas and Louisiana took place within cities and received far more attention than they otherwise would have.

"The good news is that authorities investigating these incidents have found no sign that the birds died from diseases such as bird flu. They also found no sign of parasites, poisons or other toxins.

"The bad news is that so far experts have no idea why these birds died. The birds in Beebe may have been startled into flight by New Year’s fireworks and crashed into buildings. The birds in Louisiana may have collided with power lines or cars. But none of this has been proven yet.

"Another theory is that pollution or climate change is creating stress in animals, making them more vulnerable to disease or cold weather. There is good evidence that climate change is killing frogs and salamanders, but there is little evidence of any similar effect on birds.

"So, why do mass die-offs occur? We don't know, but it is reasonable to say that we will find out eventually. And it is nice to know that nature still has plenty of mysteries for us to solve."