Science

Killer among us

There's a killer on the loose, stalking victims out of public sight and mind. Operating under the guise of the garden-variety house cat, this predator is responsible for the deaths of tens of millions of birds every year. So many birds are being killed by cats and collisions with urban America that fully a quarter of the winged species are in decline, according to the U.S. Fish and Wildlife Service.

Millions of birds die when they slam into glass office buildings or sliding-glass doors. Millions more meet their end on auto windshields. Still millions more die in crashes with communication towers, power lines and wind turbines. As reported in The Times (Dec. 8), windmills in the Bay Area's Altamont hills are taking a high toll on local birds, including golden eagles.

But house cats are the slaughter machines. One study concluded that free-ranging cats kill at least 7.8 million birds each year in rural Wisconsin alone. And that excludes urban areas. Another study in Michigan concluded that a single pet cat killed at least 60 birds in an 18-month period.

"How the devil do we deal with neighborhood cats?" wonders Al Manville, a biologist with the Fish and Wildlife Service who specializes in migratory birds. "My suspicion is that we're going to continue to see some dwindling numbers."

Fish and Wildlife's list of "birds of conservation concern" — a kind of early warning system for the avian set — grew from 28 in 1982 to 131 last year. The category does not include the 92 bird species listed as threatened or endangered.

There are an estimated 77.7 million pet cats in the U.S., according to the American Pet Products Manufacturers Assn. That's 26 million more cats than there were 15 years ago. Roughly two-thirds of them are allowed to roam outside. That number doesn't take into account the swarm of stray and feral cats, another 60 million to 100 million, says the Florida Fish and Wildlife Conservation Commission.

That's bad news for birds. Ron Jurek, a biologist with the California Department of Fish and Game who specializes in cat predation, says people often take the stance that felines killing birds is not a problem because there are so many of them flying around. "But a poacher could say the same thing," he counters.

In California, several species of endangered birds are threatened by cats, including the Western snowy plover, brown pelican, least tern and California gnatcatcher, reports the American Bird Conservancy.

Seven years ago, the conservancy decided to fight back, starting Cats Indoors!, a campaign to keep feline pets in the house.

Linda Winter, who has headed the program since its inception, said several states have adopted the program.

She also said the Department of Defense contracted with the group to devise a program for military installations because of the large cat abandonment rate by soldiers and their families transferring to other bases. Outer Banks National Park in North Carolina has asked Cats Indoors! to help in the protection of its shore birds.

"We've got thousands of activists in every state in the country," she says. The major message: Cats are not a natural part of the ecosystem. They compete with native predators and can spread disease. The conservancy also preaches that cats live longer indoors, that they hunt even if well fed and that "cat colonies" are a serious threat to birds.

Cat colonies are places where large numbers of feral cats congregate and are fed by humans. In many cases, the animals are spayed or neutered, but Jurek says that doesn't stop cats from hunting, only from reproducing.

The least tern, a coastal bird with several dozen colonies from San Francisco to San Diego, faces a threat from raccoons, foxes and dogs, but by far its biggest enemy is cats, a species far less domesticated than anyone thought.


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