BISMARCK, North Dakota — American white pelicans returned to a central North Dakota refuge in near-record numbers only to find a single island on which to nest, the U.S. Fish and Wildlife Service said.
Biologists said rising water levels swallowed one of the two main nesting islands at Chase Lake National Wildlife Refuge, home of the largest colony of white pelicans in North America. The primary nesting island for the big-billed birds, among the largest in North American, also is shrinking. But biologists aren't alarmed so far.
"We're not at all worried," said Alisa Bartos, a U.S. Fish and Wildlife Service biologist. "There is still a lot of space out there and a lot of bare ground."
An aerial count taken last week showed about 27,000 breeding adults, based on about 13,250 nests. Biologists estimate two adults per nest. A few thousand more nests were likely hidden under trees, Bartos said.
The count is among the highest recorded at the 4,385-acre refuge north of Medina. A record 35,466 birds were counted in 2000 at the refuge.
The pelicans winter mainly in the Gulf Coast states but some fly to North Dakota beginning in April from as far away as Florida and California to nest. The birds normally stay in North Dakota through September, caring for their hatchlings and feasting on crawfish, small fish and salamanders from small prairie ponds within a 100-mile radius of the refuge.
The big birds weigh up to 20 pounds, have a wingspan of nearly 10 feet, and measure 6 feet from bill to tail. The white pelican lives about 25 years, and breeds only once a year. Males and females take turns caring for their young. Typically, two eggs are laid in each nest, but only one chick survives.
Pelicans have been monitored at Chase Lake since 1905, when the birds numbered about 50. U.S. President Theodore Roosevelt designated the site as a bird refuge in 1908, when many of the birds were being killed for their feathers or shot for target practice.
Biologists have been doing aerial surveys since 1972.
Robert "Woody" Woodward, a biologist with the U.S. Geological Survey in Jamestown, said pelicans had been nesting at other islands at the refuge in the 1970s but those islands were swamped by rising lake levels long ago.
"They are way under water now," he said.
The main nesting island now was first used by pelicans in the early 1990s. Woodward said that island has shrunk from 40 acres to 8 acres in the past decade, as lake levels have risen some 8 feet in that time from snow and rain runoff, and from groundwater overflow and water that has migrated from other nearby lakes.
Some small islands are beginning to appear in the area as low points of a nearby peninsula have flooded. But none of the new islands are large enough to host the pelican rookery yet, Woodward said.