I have to disagree, Little Hawk. There is evidence that cats do a lot of damage to the wild bird population.

From the U.S. Fish and Wildlife Service

Cats

In the fall of 1990, a study on the effects of cats on wildlife was reported in the scientific and mass media. Researchers estimated that house cats and feral cats are responsible for killing approximately 78 million small mammals and birds annually in the United Kingdom.

Feline predation is not "natural." Millions of backyard birds and other animals are slaughtered by cats each year. Cats are a serious threat to fledglings, birds roosting at night and birds while they're on the nest, at the feeder and using a bird bath.

If you are unwilling to eliminate free-roaming cats, do not attract birds to your yard by putting out feeders, nest boxes and baths. Eliminating free-roaming cats is the best way you can "protect" your backyard birds from cat predation.

Responsible pet owners keep their cats indoors. Most local jurisdictions have enforceable leash laws for cats and dogs. Contact your local humane society for help.

Here's a Google search on the topic.

SRS