There are more than 90 million pet cats in the U.S., the majority of which roam outside at least part of the time. In addition, millions of stray and feral cats roam our cities, suburbs, and rural areas. So how much of a problem are these feline predators to our feathered friends? Well, quite a bit. But individual cats differ in their threat to birds. Cats that are house bound are no menace (although my wife’s cat ate my cockatiel years ago); domestic cats that have access to the outdoors have little need for wild food sources; feral cats, on the other hand, are totally dependent on wild food.
Feral cats’ diets are about 70% small mammals, about 20% birds and 10% other animals. There aren’t any clear data, but a study a few years ago indicates that cats kill at least 500 million birds a year in the U.S. More details of this study can be seen at http://dnr.wi.gov/wnrmag/html/stories/1996/dec96/cats.htm
My wife and I have had cats and a few of them did a bit of hunting, which annoyed me but it was rare. We had one cat that simply caught a bird occasionally and never hurt it. A mysterious buzzing in the garage one day turned out to be Bob the Cat holding a hummingbird by the bill, wings buzzing. It was released unharmed.
So what can cat owners do? Wild birds are pretty good at avoiding predators under natural circumstances. But bird feeders concentrate birds in a small area and provide good hunting. So, put the feeder several feet from the house (to avoid bird collisions with windows), at least four to five feet high on a post a cat can’t climb, and near some bushes or dense trees in which the birds can hide. Access to the feeder should be open so the birds can see any approaching cats. Bells on a cat’s collar are helpful as well.
I think declawing cats is cruel, but if a cat is a serious bird-killer, you might consider alternatives such as trimming the nails short or covering them with acrylic or vinyl pads.
Feral cats, though, seem to be the biggest predatory threat to birds. I have trapped several feral cats in my backyard and some were the biggest, nastiest cats I have ever seen. One was so strong I watched it bend the bars of the trap and escape – the same trap a 20 pound raccoon could not escape from. These are predators which do not belong in the environment.