Precautionary measures simply do not work. During an 18-month period, a single cat roaming a wildlife experiment station killed over 1,600 birds and small mammals. A study in England showed that cats wearing bells killed more birds than cats without them; during a study in Kansas, a free-roaming declawed cat killed more birds than the cats with claws.The Audubon Society recommends bibs. Apparently they are effective, maybe because the cat feels so embarrassed.
The June 2009 Scientific America includes "The evolution of house cats":
Recent genetic and archaeological discoveries indicate that cat domestication began in the Fertile Crescent, perhaps around 10,000 years ago, when agriculture was getting under way.