In the breeding season, waterfowl can become aggressive. Particularly when defending a nesting territory or hatchlings. If you are planning a new addition to your pond, it pays to talk to other breeders of the waterfowl you’d like to keep.
Dominant and beligerent species can even prevent others breeding. Some are just plain mean all the time, like this Feugian Steamer Duck.
Pics from Charlie Hardcastle, Zoe Brodie James, Phoebe Vaughan, Morag Jones, Jed Dwight