Whoa up, Dragline. The deal is not about Darling Fluffy in the usual urban/suburban setting. It's about feral cats outside of those areas. Feral cats are extremely destructive against squirrels, rabbits, songbirds and quail. That is known fact, not subject to debate.
A study done some years back by the Wisconsin wildlife agency and reported on in (IIRC) Sports Afield magazine concluded that feral cats in rural areas kill approximately 100 songbirds each, per year. The study's estimate of the feral cat population in Wisconsin was approximately one million.
I'm in a rural area in south Georgia. I had noticed a decline in squirrels, rabbits and birds around the immediate area. I learned that a nearby neighbor had nearly a dozen house cats. She had catfood in bowls outside, 24/7/365. The local animal shelter got involved and did the Havahart trap thing for a few months. 72 house cats. We're seeing the beginnings of a comeback in squirrels and birds.