Going into town yesterday I saw two dead cats on the highway, one was an orange tabby and one was a black cat with white stockings . I used to 'agree to disagree' with a friend I worked with about a cat's need to go outside. She said they had to, it was part of their nature, so she let her cats roam at will. I have a cat I love to distraction. And we live in a wooded area with coyotes, raccoons, cars and foxes. All are lethal to cats. I have never been able to understand how people who love their pets could care so little about their safety. There used to be a couple of cats running free in our neighborhood. I haven't seen either of them in months. It's hard to tell what happened to them - did their owner's move? Or did they run into something they were not equipped to handle? An article by Scott Shalaway enumerates the many dangers that cats face while running free outside - and some suggestions for keeping your indoor cat happy.
Cats are notorious for hunting songbird young. There is no defense for a fledgling robin from a hunting cat and the bird's parents cannot protect him. This New York Times article "Give Birds a Break. Lock up the Cat." quotes studies about cat predation on songbirds.
If you are on the fence about letting your cat out, please, keep him/her in. Your cat will live years longer than a cat allowed to run outside and who doesn't want that?