NYTimes.com: Tweety Was Right: Cats Are a Bird’s No. 1 Enemy
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.
By contrast, 440,000 birds are killed by wind turbines each year, according to the United States Fish and Wildlife Service, although that number is expected to exceed one million by 2030 as the number of wind farms grows to meet increased demand.
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.
You always here about the number of birds killed by turbines but not the amount killed by cats. I wonder how they came up with the number 500 million.