I think part of the decline of american birds is the well fed house cats that can afford to hunt for sport, as opposed to just what they need to eat... So pit a human fed cat against birds that have to struggle for their own food (unless someone's feeding them close by as well.)
This seems illogical to me. Cats like to play, of course, but their reason for hunting is to eat. If they're not hungry, they will hunt way way less, don't you think? And you think the birds are in some kind of weakened state because they are doing what they do, and the cats are super-cats because they are fed by humans?

I have two cats in my yard, and rarely ever see them catch birds or find dead birds in the yard. They do, in fact, sometimes kill birds, but not nearly to the extent that they are decimating the local bird population. I scared away about 30 doves off the edge of my pool the other day--it was amazing. All the stray cats in the neighborhood couldn't have taken care of that bird population. (My dog hunts birds every single day, but she never catches them. )

I agree with Mimi that it's development and loss of habitat that hurts the birds. Cats are just part of the food chain.

Karen