Cat owners. bird lovers and property owners, Lend me your ears!
"Once upon a time, I was known as the neighborhood "Cat Woman." Not because I was Batman's adversary. Rather, I just couldn't resist taking in stray kitties. I housed and fed as many as twenty cats and kittens at a time. Many of them were offspring from the initial fugitive felines seeking safe asylum in my big red barn."
snip..........
"My understanding then of predator and prey relationships in nature was simple and misguided. I viewed predation as a natural phenomenon. Predators hunt and kill, and prey utilize evasive maneuvers to avoid getting caught. It's natural for cats to kill and so I thought that birds and other local wildlife had built-in defenses against their predation. I couldn't have been more wrong. My reasoning was missing an extremely important variable called evolution."
Snip......
Slowly I had to come to the realization that by allowing my barn cats to roam free, I was placing a higher value on their freedom than on the life of the animals they killed. In the early 1990's, I stopped allowing my cats to venture outdoors. The diversity of birds in that neighborhood still has not recovered and maybe never will. I know that other factors may have contributed to this decline, but I cannot disregard the impact from my ignorance.
http://www.matrifocus.com/LAM02/earth.htm