Times Quotes Biologist Likening Cats to Kudzu

Reporter Elisabeth Rosenthal has found another unlikely environmental menace: Cats, an invasive species that disturbs the natural order, like kudzu. That's the takeaway from Monday's report on the grave danger felines present to birds: "Tweety Was Right: Cats Are a Bird's No. 1 Enemy."

While public attention has focused on wind turbines as a menace to birds, a new study shows that a far greater threat may be posed by a more familiar antagonist: the pet house cat.

A new study in The Journal of Ornithology on the mortality of baby gray catbirds in the Washington suburbs found that cats were the No. 1 killer in the area, by a large margin.

Nearly 80 percent of the birds were killed by predators, and cats were responsible for 47 percent of those deaths, according to the researchers, from the Smithsonian Institution and Towson University in Maryland. Death rates were particularly high in neighborhoods with large cat populations.

Mr. Marra won't make friends among cat-lovers with thoughts like these:

"Cats are way up there in terms of threats to birds - they are a formidable force in driving out native species," said Peter Marra of the Smithsonian Conservation Biology Institute, one of the authors of the study.

The American Bird Conservancy estimates that up to 500 million birds are killed each year by cats - about half by pets and half by feral felines. "I hope we can now stop minimizing and trivializing the impacts that outdoor cats have on the environment and start addressing the serious problem of cat predation," said Darin Schroeder, the group's vice president for conservation advocacy.

Rosenthal then offered a fact, inconvenient to environmentalists, that "440,000 birds are killed by wind turbines each year," a number expected to grow as wind farms become more prevalent, before turning the mike over to Marra:

Household cats were introduced in North America by European colonists; they are regarded as an invasive species and have few natural enemies to check their numbers. "They are like gypsy moths and kudzu - they cause major ecological disruption," Dr. Marra said.