I have free ranging cats in my neighborhood that I have seen kill adult rabbits. These are pets that are allowed to roam, not feral cats, so they are well fed. I have no doubt they could kill one of my chickens. In fact, they don't have to actually kill your birds outright, as cat saliva can carry bacteria that are toxic to many birds -- they only have to be bitten, and will probably succumb to infection w/o treatment. I feel no differently about fee range cats than i do about roaming dogs -- its irresponsible pet ownership. Any cat caught in my yard (live trap!) goes home with a collar and a note - keep me inside or i go to the pound! In a rural situation it may not be quite so straightforward, as there are so many "unowned" cats, but IMHO, they are all a menace to not only chickens but to wildlife. I feel no sorrow about taking them to the shelter. They kill BILLIONS of native bird every year. It's not their fault - they are just following their instincts, but frankly they are no different than any other introduced species - starlings, garlic mustard, wild hogs, burmese pythons in the Everglades - they are all a threat to native wildlife. BTW - I love my cats - INDOORS!