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Out of danger: US peregrines stage a comeback. Credit: NIALL BENVIE/BBC NAT. HIST. UNIT

The US interior department last week proposed removing the peregrine falcon from its list of endangered species. This would be the first time in three years that a species has been ‘delisted’ because of a dramatic recovery in numbers.

The peregrine is the first of about two dozen species scheduled to be taken off the list in the next two years, following a directive in May by interior secretary Bruce Babbitt to expedite delistings.

More than 1,100 animals and plants are protected under the Endangered Species Act (ESA). But only 27 species, subspecies or populations have been taken off the list since the act came into force in 1973.

John Fay, a biologist at the endangered species division of the US Fish and Wildlife Service, says: “We're pretty conservative about calling something recovered.” Because some endangered populations had been declining for as long as a century before the ESA was enacted, he says, “after 25 years it's unreasonable to expect a lot of recoveries”.

The service has lacked the resources to devote to delisting, having only recently recovered from a congressional moratorium on new listings in 1995 that created a backlog of species in need of protection.

The peregrine has bounced back from a low of 324 nesting pairs in 1975 to at least 1,593 breeding pairs in the United States and Canada. The comeback is due more to the banning of the pesticide DDT in the 1970s and to an aggressive captive breeding programme than to ESA protection. This has led congressional critics to attack Babbitt for touting the peregrine and other delisting candidates as ESA success stories.

Last month, 30 members of the Western Caucus, a conservative group of property rights advocates in the House of Representatives, wrote to Babbitt challenging his statement in May that the ESA has been proved a success. Some species are being removed from the list, they point out, only because they have become extinct or have been reclassified, and others are being delisted because their population estimates have grown as scientists discover more of them in the wild. Most biologists and wildlife managers support delisting in principle, but urge caution.