Putting bells on cats doesn't work. Cats stalk slowly and often wait in ambush to catch their prey. There is no time for the bird to escape when it hears the bell, if it hears the bell. Birds and other wildlife do not associate bells with being stalked.

The Pet Food Institute estimates that there are at least 65.8 million pet cats in the U.S., and another survey indicates that only a little over half of these are kept indoors.

Ground-nesting birds are very susceptible to free-roaming cats. So are young birds that leave above ground nests and spend a few days on the ground learning to perfect their flying skill.