My drake is 18 mths old and he is half Pekin and half Mallard. He is starting to mount the other 2 females and he also started this dip of his head followed by a half second very high pitched squeal. He does this at all different times, when alone, in the pool, with the others, while grooming, swimming out in the yard, playing with his toys,...I do not see any constant that it could be related too,..does anybody else's ducks do this and if so do you know what it means?