HILTON HEAD ISLAND -- State and federal wildlife officials are investigating the deaths of hundreds of sea birds turning up on the coasts of South Carolina, Georgia and Florida.
Wildlife biologists say more than 1,000 shear-waters -- large, gull-like water birds that spend most of their lives far offshore until they nest -- have been found dead over the past two weeks on Southeastern beaches.
Since last week, more than 160 of the dead birds have been found in South Carolina, including at least 22 on Hilton Head Island.
Officials remain uncertain about what's causing the mass casualties, but they say most of the birds recovered appear to have died of dehydration and malnutrition during migration.
Most shearwater carcasses recovered in South Carolina appear to be those of juvenile birds, said Craig Watson, a wildlife biologist with the U.S. Fish and Wildlife Service in Charleston. A few have been found alive.
"For some reason, these birds are dying, and most think it's due to starvation," he said. "Whatever the reason, this appears to be pretty significant; we just don't know how significant yet."
Preliminary findings in Georgia and Florida indicate no pathogen or disease -- including West Nile virus or avian influenza -- is involved in the deaths, biologists said.
Biologists from the Southeastern states are working with federal agents to collect, tabulate and test bird carcasses to determine a cause.
The problem surfaced in Florida about two weeks ago, and it's worked its way north since then, biologists said.
So far, more than 600 dead shearwaters have washed ashore in Florida, and at least 100 were reported in Georgia.
"The only common factor is that most of the birds are emaciated and pretty much wasted," said Dr. Al Segars, an S.C. Department of Natural Resources veterinarian who's helping coordinate efforts here to collect carcasses.
Each year, the birds migrate more than 7,500 miles from their breeding grounds on an isolated group of islands in the South Atlantic to northern North America and Greenland.
Typically, the birds pass by South Carolina far offshore, biologists said.
"Unless you're a fisherman and out by the Gulf Stream, you're not going to see these birds in South Carolina," Watson said.
He said the birds tend to flock together in groups of 50 to 100 and fly closer to the water than most migrating birds. They often congregate around fishing boats.
A similar die-off was reported in 2005, when dead birds washed up on beaches from Florida to Virginia.
"It's not uncommon for some of these birds to die off during migration, but the numbers here are significant enough to cause alarm with natural-resources people internationally," said Jennifer Koches, a spokeswoman for the U.S. Fish and Wildlife Service in Charleston.
"No bird can sustain this type of die-off year after year."