Will Kincaid  /  AP
Thousands of white pelicans and their nests were on these two small islands in the middle of Chase Lake National Wildlife Refuge, N.D., when this photo was taken last May.
updated 7/13/2005 2:31:32 PM ET 2005-07-13T18:31:32

The Fish and Wildlife Service is investigating the deaths of thousands of young white pelicans at a wildlife refuge in central North Dakota, a year after thousands of adult birds abruptly left the same location.

At least 8,000 chicks may have died over the past two months, said Ken Torkelson, a spokesman for the Chase Lake National Wildlife Refuge.

“The difference is, last year the adults left first,” he said. “This year, the young have died and the adults have no reason to stick around.”

Severe storms or a disease outbreak may have caused the mass die-off, said Marsha Sovada, a biologist at the U.S. Geological Survey’s Northern Prairie Wildlife Research Center in Jamestown.

The Fish and Wildlife Service said an inspection of the refuge last week indicated only about 500 chicks left from a nesting period that could have produced as many as 9,000 of them. All but about 2,000 adults had left, from a population estimated at 18,850 in late May.

Earlier exodus still a mystery
Officials had hoped the refuge would return to normal after nearly 30,000 adult pelicans took off last year, leaving their young behind. Officials still can’t determine what caused last year’s exodus.

The white pelican, one of the largest birds in North America, breeds only once a year, and males and females take turns caring for their young. The birds have a wingspan of nearly 10 feet and live about 25 years.

The white pelican colony at the 4,385-acre Chase Lake National Wildlife Refuge north of Medina has been the largest in North America, peaking at 35,466 birds in 2000.

The pelicans normally stay at the Chase Lake refuge through September, raising their young and feasting on crawfish, small fish and foot-long salamanders from small ponds known as prairie potholes.

Samples have been sent to the National Wildlife Health Center in Madison, Wis., to try to find out what killed the young birds at Chase Lake.

The chicks that remain at the refuge are still being cared for by adults, Torkelson said. The chicks remaining at the refuge appear to be healthy, Sovada said.

Electronic tags on some
Biologists have attached backpack-like electronic tracking equipment to eight pelicans to monitor their movements when they leave the colony, and plan to fit two more with the equipment.

Sovada said large die-offs of pelican chicks also have been reported this week at Medicine Lake National Wildlife Refuge in northeast Montana and at Waubay National Wildlife Refuge in northeast South Dakota.

“It could have no relation to what’s happening at Chase Lake,” she said.

The West Nile virus likely is to blame for the chick deaths in Montana and South Dakota, Sovada said.

Other pelican nesting colonies have had high chick mortality rates in the past three years, Torkelson said.

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