It is amazing the demons that they become over their eggs and babiesThe huff puff sounds are conversation. I know it sounds aggressive, but they really are just talking. the pant nibbling is curiosity and a social action. They also head bob, raise the crests on their heads, wag their tails. If a Muscovy is acting aggressively, it holds its mouth open, and follows your movement followed by a jump towards you and flogging. Usually this is a female that does not want you near her babies or eggs! I have one mother scovy duck, Physco that is aggressive over her nest. She will take on goats, pigs you name it! She has been impossible to confine and always nests in the goats house. Off season, she is a perfect little lady.