My chocolate 2yr old cocker has done the same on a pheasant shoot. She's been doing brilliant on her first season. But a very wet day recently with lots of pheasants in a thick hedge. The birds were wet so we're running not flushing and she pegged one I couldn't get in the hedge to scold her. She came out retrieving the pheasant to hand looking very pleased with herself. I ignored her took the bird off her dispatched it. Training excercises since that have been her sitting up and me throwing tennis balls all round her and telling her to leave . Then calling her away or picking them up myself.