That's a weird thing, by the way...
Given the vast variety of birds, which to the best of my knowledge, almost all have no teeth at all, it must have been a severe liability at one point, or perhaps lack of teeth is coincidentally linked to a gene that supplies a very high survival factor, like wings.
Otherwise, you'd think at least SOME birds would still have teeth. (I think there's one weird one that does, but I'm too lazy to look it up.)