Definitely make sure you start antibiotics. Any scrach or bite ive gotten from my kitties has taken weeks to heal... But ive seen much worse pictures of attacks and beatings on here that the ducks have survived. At the same time though, I feel bad for the kitty...just doing what she can to survive...you are probably either going to have to take the cat to a shelter or start feeding it. If she has a full tummy, she'd prob have no reason to attack the birds since it sounds like they have lived there for a while...