How long can a bird live after a cat attack?

My cat attacked a baby pigeon and has done some serious damage to the bird. I wouldn't have expected it to last as long as it has already, but I gave him a little wash with clean warm water and wrapped him in a warm towel and he is still alive (that was about 3 hours ago). He really does have some serious injuries - lost half a wing, has several deep gashes on his side and under his belly and a decent hole in his throat. (I could see his breakfast!) I really doubt he'll live, what should I expect, and how can I help him?