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Winter raptors return to Colorado

Camera Environment Writer
Thanks to a potent pesticide, bald eagle populations plummeted to an all-time low in the early 1960s. Now, more than 30 years later, the United States is in the midst of a raptor baby boom. After DDT was banned and the Earth's immune systems washed most traces of the poison away (in North America, at least), the majestic eagles are on the rebound. Rising like the phoenix from the ashes, eagles in the United States have increased from 450 nesting pairs in the early 60s to more than 4,000 now. They have reclaimed territory that was abandoned as the raptors died off. About 23 of those pairs live in Colorado year-round, said Jerry Craig, raptor biologist for the Colorado Division of Wildlife. And the trend continues upward.

Colorado has two populations of eagles. One is the resident population; the other is migratory, wintering in Colorado, which provides a southern getaway for residents of the Northern states and Canada. Colorado has never been prime eagle habitat, according to Craig. "Historically, Colorado never has had the extensive habitat that lake states and others have had," he said. The highest concentration of eagles in the state is in the northwestern corner along the riparian habitat provided by the Colorado, White and Yampa rivers.

However, metro area bird watchers have noticed the migratory increase. "It really is a magnificent bird," said Hugh Kingery, who teaches a birding class for the Denver Audubon Society. "For one of our beginning birding classes we went to Chatfield (Reservoir, south of Denver) and the first bird they saw was a bald eagle. That really thrilled them. I think it made permanent birders out of most of the class."

Moving back

The eagles are reclaiming what remains of their habitat, which means the population will continue to increase for a while, Craig said, adding that the raptors have shown amazing adaptability. "They're fairly tolerant of people.....they have to be," he said. Their recovery was nothing short of amazing. Once the poison was purged, their "reproductive difficulties disappeared rather quickly," he said. Thinning egg shells related to DDT in fish and other prey contributed to low birth rates.


Another problem that was recently addressed was the lead shot used by waterfowl hunters in their shotguns. Lead shot was banned and a substitute found, Craig said. Even with perfect conditions, however, Colorado terrain will limit the population. "I would never anticipate more than 30 (resident) pairs in the state, but you never know....they're learning," he said.

As development eats up habitat and destroys the prey base, the numbers will, inevitably, begin once again to decline, he said. Eagles prefer waterfowl, he said. But, when times are bad, they depend on prairie dogs to pull them through. Development is infringing on both sources of food.
But the decline won't be dramatic.
"It's really insidious and difficult to lay a hand on what will be the straw that breaks the camel's back," Craig said.


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