My second post: Corinna, your cats are nowhere near so successful as the feral cats my neighbor feeds. After I lost a pair of Mockingbirds and a Bluejay that had been nesting here for years I stopped going out in my yard completely.
My garden and flower beds were plowed under, and my grand children's sandbox taken apart. I hire my yardwork done now.
I go to my garage to check and reset my Havaheart trap several times daily, and transport the cats to Animal Control.
Even one bird or native animal killed is too many, when it is killed by an unwanted domestic pet!
Cats are a pet species, and as such should never be abandoned into the wild, much less be subsidize fed and enabled to predate on our wildlife, and compete with our natural predators. The killing of our fauna by pets is anything but compassionate, humane, and non-lethal!