May 18, 2009

Bald Eagles Running Off Bird Population

After years of decline, bald eagles are springing forth with an aggressive appetite for great cormorant chicks.

It's a phenomenon that threatens to wipe out the U.S. population.

Some believe the eagles are finding less fish to eat and instead flying to Maine's remote rocky islands where they've been raiding the only known nesting colonies of great cormorants.

In fact, the eagles are causing the numbers of the shiny black birds to fall from more than 250 pairs to 80 pairs since 1992.

"They're like thugs. They're like gang members. They go to these offshore islands where all these seabirds are and the birds are easy picking," said Brad Allen, a wildlife biologist with the Maine Department of Inland Fisheries and Wildlife. "These young eagles are harassing the bejesus out of all the birds, and the great cormorants have been taking it on the chin."

Since the 1960s, the bald eagle recovery has been amazing. They have grown from 400 pairs to more than 10,000 pairs in the lower 48 states.

Bird experts say eagles are opportunistic feeders and will go after the easiest prey they can find. Many eagles have shifted their diet from fish to seabirds in Alaska, and in the Midwest, they've been known to eat baby blue herons.

But the great cormorants are more worrisome, because their numbers in Maine are so small, said John Drury, of Vinalhaven, who's been counting seabirds on Maine islands for more than 25 years.

Last summer Drury counted only 80 great cormorant nests, the smallest number since 1984, and without protection he fears the Maine population could be wiped out.

He said that so far little has been done for great cormorants in the way of protection.

"We like to have diversity of species," Drury said. "If we're going to spend all that time and energy to protect terns, then cormorants deserve as much attention."

There are now more than 10,000 pairs of bald eagles, according to the U.S. Fish and Wildlife Service.  Maine's 500 pairs represent the largest population in the Northeast, up from less than 30 pairs in the 1960s

Governor John Baldacci is set to sign a bill this month taking it off Maine's endangered and threatened species list.

The bald eagle was taken off the federal endangered species list two years ago, but all those eagles need to eat.

Eagles have also been seen eating loon chicks and carrying off adult loons, said Sally Stockwell, director of conservation at Maine Audubon.

If the eagles' natural diet of fish were more plentiful, perhaps they wouldn't be so inclined to go after other birds, Drury said.

"They'll catch whatever is easiest to catch," he said. "There are more birds now and less fish."


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U.S. Fish and Wildlife Service