My sons and I have been managing a mixed flock composed of one Toulouse Goose, two Pekin ducks and four Buff Orpington Chickens. They spend the nights together in an off-of-the-ground chicken/duck house we built. They are between four months and a year old. During the day, the chickens range separately over an acre of grass, trees and brush. The goose and two ducks stay together and range over the same land, but separate from the chickens. We also have a acre size pond where the ducks and goose will swim. The goose is clearly the leader among the webbed-foot crew and always puts herself between the ducks and potential danger. The ducks will never stray from her side. No issues; just a big happy family until a month ago. Then all of a sudden, one day the goose started trying to hold one of the duck's head under water in the pond. It was a pretty aggressive effort and we thought the duck might drown until we went out in the boat to break it up. Since then, there has been no more of that, but we note the goose will bite the same duck's head to the point of the duck missing a lot of feathers on the back of her head. This happens every couple days and lasts just a few minutes. The goose hollers when she does this as if she is angry at the duck for some type of infraction. The duck just seems to roll with it. The other duck is left alone. Both ducks still seem to admire the goose. And, if we separate the hurt duck from the goose, they get upset and make a lot of racket, especially the goose. Wondering if there is anything we can do to arrest this behavior. Does it stop at some point? We've done some research; the behavior does not seem to be repeated in the way we see it happen in the literature we have studied. Hope it doesn't end bad for the duck. Thanks for reading.