Why do you so often see pigeons missing one or two toes?

Do they peck each other's toes off in fights? I mean.. How? You rarely see any other birds missing a toe.

There's one pigeon that I see a lot outside where I used to work. I'd feed it bits of bread on my lunch break. It had only TWO toes. One leg was just a stump that it couldn't really balance on and the other consisted on one front toe and the back one.

So.. Anyone got an explaination?