The bald eagle has made a soaring comeback from the edge of extinction but wildlife experts in two Western states are concerned that eagle populations may be poised for a nose dive.
The Fish and Wildlife Service is expected to drop the national bird from the federal list of threatened and endangered species in June.
Environmentalists and scientists widely support the move because of the species' success since a 1972 ban on the pesticide DDT and since it was protected by the Endangered Species Act in 1978.
Still, some eagle experts are worried, warning that the Bald and Golden Eagle Protection Act, the law that will protect bald eagles after delisting, does not adequately shield the nesting trees and feeding perches eagles depend on.
"Eagles shouldn't have to go through a population decline, which is definitely going to happen after they're delisted," said Steve Sheffield, a professor at Virginia Tech University and conservation committee chairman with the Raptor Research Foundation.
Bald eagles have climbed to 9,000 breeding pairs from 417 pairs in 1963, when they were on the brink of extinction.
Idaho, Arizona numbers fall
Yet in Idaho, the number of eaglets produced per pair of nesting bald eagles in 2006 was the lowest in 12 years. That combines with a steady increase since 2000 in nests without young, Idaho Department of Fish and Game figures show.
In Arizona, a modest eagle population failed to produce enough offspring to replace itself nine of the past 10 years, according to the Southwestern Bald Eagle Management Committee.
Jody Millar, bald eagle monitoring coordinator for the Fish and Wildlife Service, said that while there is "certainly not a total absence of issues concerning eagles, the overall progress outweighs local issues."
In Idaho, biologists have just begun to take steps to determine what is causing eagle productivity to plummet.
"At no point should we relax. If that's the direction we're going, we could see a complete crash," said Rex Sallabanks, non-game bird program coordinator for Idaho Fish and Game.
While Idaho has seen the number of bald eagle pairs grow from 11 to 200 since 1979, Arizona is home to a fragile population that has required active intervention by biologists to expand from 18 pairs in 1985 to 50 last year.
Lawsuit to keep listed
The Center for Biological Diversity and the Phoenix chapter of the National Audubon Society are suing to keep the state's eagles federally protected. They say the case threatens to derail the national delisting effort.
In Arizona, the state with the fastest-growing human population, "the eagle population is very small and very vulnerable and the habitat it depends on is extremely threatened," said Kieran Suckling of the Center for Biological Diversity.
Scientists say the emerging trends, with suspected culprits ranging from human disturbances to environmental contamination, require study even after delisting. "We're not sitting here thinking we shouldn't be cautious," said Greg Beatty, U.S. Fish and Wildlife Service biologist in Phoenix.
While some eagles are surprisingly tolerant of human activities around nests, most thrive along shorelines and river banks that remain largely intact because of habitat protections guaranteed by the Endangered Species Act.
The Bald and Golden Eagle Act bans killing and disturbing the birds without spelling out what constitutes a disturbance. Now the Fish and Wildlife Service says it is seeking to toughen the provision that prohibits disturbing bald eagles while at the same time giving broader leeway to developers, energy interests and timber companies that have waited decades to launch projects in eagle habitat.
The government argues establishing a program that would legally permit harm to eagles or their nesting areas amid activities such as logging and mining is a sign of the eagle's resilience. "With a recovered species, the regulatory environment should be reduced to make reasonable accommodations," said the Fish and Wildlife Service's Millar.