Fishkeeper
Crowing
Wow. No.
First, if it's not badly injured, it'll probably be fine. Second, even if it was badly injured enough to make a mercy kill the best option, you could put that a bit more gently.
For anyone reading this that any small animal which has been caught by a cat needs to be taken to a wildlife rehabilitator for antibiotics. Cats have bacteria in their saliva, easily spread to their fur and claws, that have a high infection rate and a very high lethality rate on small animals like birds and reptiles. This is why you need to keep your cats away from your small pets, and from baby chicks.
Dogs can also cause infections from bacteria in their mouths, but are less likely to do so. It may be good to take the bird to a wildlife rehabilitator if you have any in the area, but from your description it should be okay. The fact that it's improving means it probably doesn't have an infection.
