By Darryl Fears
Tuesday, March 15, 2011; 5:03 PM
Cats stalking adorable and helpless birds is the stuff of cartoon legend, starting with the lovable Tweety Bird.
But a study of bird kills by domesticated house cats in the District suburbs found that it is no laughing matter.
The study, published recently in the Journal of Ornithology, chronicled predatory behavior by free-roaming cats that happens many times over in cities and suburbs nationwide, resulting in up to a half-billion bird kills each year.
Domesticated cats pounced on baby birds, often after they first flew from their nests, at three sites that were studied in Takoma Park and Bethesda, wreaking havoc on local ecosystems.
"Cats are predators, non-native predators," said Peter Marra, a research scientist at the Migratory Bird Center of the Smithsonian Conservation Biology Institute. "Cats are the only domesticated animal that's allowed to roam free," Marra said. "Cats need to be put indoors. They cause major reductions in a number of animals and birds."
Researchers for the study, published in January, followed a gruesome trail of bird kills in Spring Park and Opal A. Daniels Neighborhood Park in Takoma Park and Bethesda. They climbed trees, checked nests, studied eggs and tied transmitters to birds that in some cases continued to send signals where the house cat killed them.
A culprit was not located for all bird deaths, but "fledglings found with body damage or missing heads were considered symptomatic of cat kills," the study said. Seventy-nine percent of all bird deaths at the three sites were fledglings.
"Birds do provide a variety of service to ecosystems," Marra said. "They spread seed. They're pollinators. They provide a sense of place. Robins are now singing, providing a much healthier environment and a nicer place to be."
A few dead birds here and there might not seem like a big deal, Marra said. But the deaths add up.
There are about 77 million pet cats in the United States, according to the American Bird Conservancy, and about a third are kept exclusively indoors. They kill about 500 million birds yearly.
Another 60 million to 100 million undomesticated cats kill even more birds. A University of Nebraska at Lincoln study, Feral Cats and Their Management, estimated that feral cats kill 480 million birds yearly in the United States and are responsible for wiping out 33 species worldwide.
Feral cats - also known as "alley cats" - wiped out the wren on New Zealand's Stephens Island in 1895 and today threaten bird species on the Hawaiian islands, according to the study.
Marra said some animal rights groups and cat lovers are adamant about allowing all cats to roam free. "They defend cats like you wouldn't believe," he said.
But the People for the Ethical Treatment of Animals is not among them.
"What, do you love animals but you don't care about wildlife? It's ridiculous," said Martin Meresereau, PETA's director of emergency response.
"The list of reasons why we want to keep our animal companions inside with us is limitless," Meresereau said. Free-roaming house cats are too often nabbed by people who use them to train fighting dogs or sell them to research labs.
"I've gotten a dozen cruelty workers with cases stacked up to the ceiling, and the majority of those are cats," Meresereau said of cats that were allowed to roam outdoors.