Human activity - the using and banning of particular chemicals - is helping some birds of prey and hurting others along three Western flyways that researchers are watching to gain insight on the environment.
"Our main purpose in this is long-term. What we really want to know is environmental trends," said Steve Hoffman, founder, president and director of Albuquerque-based HawkWatch International.Birds of prey make fine environmental barometers because they feed at the top of the food pyramid, making them sensitive to environmental changes.
Fewer birds of prey might signal ecological damage that could threaten the quality of life for other species, including man, Hoffman said.
Raptors "are not only worth preserving as an environmental barometer, but also for their intrinsic value. They're part of our national heritage," he said Thursday.
The birds also are part of the complex ecosystem, "and for the ecosystem to function in a healthy manner, all those components need to be in place," Hoffman said.
Raptor conservation is a tremendous challenge, he said.
Conservationists are concerned with securing food and habitats over the birds' massive migration area, their breeding grounds and their wintering grounds, Hoffman said.
HawkWatch, formerly the Western Foundation for Raptor Conservation Inc., has been counting birds of prey along the Rocky Mountain, Intermountain and Pacific flyways.
It has three monitoring sites in the Rocky Mountain Flyway - one near Denver, one in the Manzano Mountains southeast of Albuquerque and one in the Sandia Mountains east of Albuquerque.
The Intermountain Flyway is monitored in the Goshute Mountains west of the Bonneville Salt Flats and the Wellsville Mountains northeast of the Great Salt Lake.
The Pacific Flyway is monitored near the Golden Gate Bridge in San Francisco by the Golden Gate Raptor Observatory, which shares its counts with HawkWatch.
HawkWatch is working on statistics collected during the past several years to prepare a report for the U.S. Fish and Wildlife Service next May.
"Our preliminary results suggest six species appear to be increasing and three may be in trouble," Hoffman said.
The northern goshawk, the prairie falcon and the golden eagle appear to be in trouble in the West, he said.
"With the northern goshawk, the loss of forest habitat is our main concern," Hoffman said.
"With the prairie falcon, our main hypothesis is the increase of the common raven," he said. "Human activities - road kills, dump sites - make food very available to ravens.
"They also nest on cliffs, which is where prairie falcons nest. Ravens nest first in many cases, and they may defend the area around the nest.