Googling "cat predation" pops up a bunch of sites, many quoting the same study. These are house cats. I know of at least one group which advocates capturing feral cats, neutering them, and then releasing them back to the wild. That makes no sense to me.
Here's an excerpt from one site on ?responsible cat ownership:
Cat Facts - Effects of House Cat Predation on Our Native Wildlife
While many cat owners may believe that their pet cannot possibly have a significant impact just because it hunts, the cumulative devastation of cat attacks on wildlife is substantial. With many species in danger due to habitat loss, predation by our house cats is yet one more hardship we humans impose on wild animals already struggling to survive.
Isn't hunting by cats a natural thing? While it may be instinctive for a cat to hunt, house cats are not native to North America and they cause an imbalance in the ecology of an area by killing so many wild animals. Because their population numbers are artificially large due to being kept as pets, cats are far more common than natural selection would normally allow native predators, such as fox or bobcat, to be. Predators are supposed to be rare, not abundant, in nature.
Consider these studies:
Researchers studying 70 cats in a small English village estimated that pet cats in England were responsible for killing 70 million native animals per year, including 20 million wild birds.
In a study of radio-collared farm cats in Wisconsin, researchers Stanley Temple & John Coleman estimated that each year cats kll at least 19 million songbirds and 140,000 game birds in the state of Wisconsin.
A researcher at Point Reyes Bird Observatory in California, noting that there are approximately 55 million cats in the U.S., of which 44 million are permitted outdoors, suggested that the toll may be as high as 4.4 million songbirds per day in the U.S.
Cat predation can also negatively impact our native predators, especially hawks and owls. A study in Illinois concluded that cats wwere taking 5.5 million rodents and 2.5 billion other vertebrates from a 26,000 square mile area, effectively depleting the prey base necessary to sustain wintering raptors and other native predators.
Animal intake data from wildlife rehab centers across the U.S. corroborates the toll of cat predation that the above findings document.
Overwhelmingly, cat predation (including cat attack cases and animals orphaned by cats) is the single largest reason for admission to many wildlife centers. Typically, less than 10-20% of cat attack victims survive. Even when external damage appears minor, there is usually massive internal hemorrhaging & sift tissue damage from crushing and even minor puncture wounds expose the victim to over 60 types of bacteria known to exist in cat saliva.
The Migratory Bird Treaty Act protects native birds from being killed or kept by people. Any person who willfully allows his or her cat to injure or kill migratory birds is, in effect, in violation of this federal law. While this may seem like an extreme interpretation of the law, the "sport" hunting of wildlife by our well-fed pet cats is a waste of life.