Seabirds’ die-off puzzles scientists – 07/07/2007

Atlantic (juvenile) bird die-off – malnutrition

Seabirds’ die-off puzzles scientists
Tides carry waves of carcasses after harsh migration
By Peter Frost – McClatchy Newspapers

HILTON HEAD ISLAND –State and federal wildlife officials are investigating the deaths of hundreds of seabirds turning up on the coasts of South Carolina, Georgia and Florida.

Wildlife biologists say more than 1,000 shearwaters – 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 seem 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 small percentage 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.”

Biologists from the Southeastern states are working with federal agents to collect, tabulate and test bird carcasses to determine a cause.

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.

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, said Dr. Al Segars, a S.C. Department of Natural Resources veterinarian who’s helping to coordinate efforts to collect carcasses.

Sometimes, he said, they just run out of gas.

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, usually near the Gulf Stream or farther east, 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.

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.”

To help
The S.C. Department of Natural Resources requests that people who find a dead or sick shorebird:

Record the location, date, time and species found and send information to Dr. Al Segars at: segarsa@dnr.sc.gov. Leave the bird where it was found.

If live birds are found, do not attempt to catch or handle. Seabirds can inflict stabbing injuries. Attempting to handle them also can cause the bird to injure itself.

Greater shearwaters are gull-like in appearance, reaching 17 to 20 inches in body length with a 3- to 4-foot wingspan. Adults weigh about 2 pounds.

Their bodies are mostly brown in color with a white underbelly and neck. The birds have black, hooked bills with visible nostrils; pink, webbed feet, and dark spots just under the wing.

Shearwaters breed in the Southern Hemisphere at a group of isolated islands between southern South America and Africa called Tristan da Cunha.

Each year, they migrate more than 7,500 miles to portions of North America including northern New England states and Canada and farther north near Greenland. Shearwaters spend most of their lives far offshore and are rarely seen in South Carolina.

The birds fly close to the ocean with stiff wings and few wing beats.

They feed on squid and other fish, which they catch from the surface or by plunge-diving.

Sources: University of Maine, United States Geological Survey, Nova Scotia Museum, S.C. Department of Natural Resources