Duck vs Goose

Not quite, though they are close relatives in the same family. Geese are a distinct group within the waterfowl, sitting between the ducks and the swans in size and proportion, and they differ from ducks in more than just being bigger. Geese have longer necks, walk and graze on land with legs set further forward, show no strong plumage difference between the sexes, form long pair bonds, and share the raising of the young. Ducks, by contrast, are more water-bound, more sexually dimorphic, and mostly leave brood care to the female. So a goose is not simply a large duck; it is a bird with its own set of adaptations for a more terrestrial, more family-oriented life.

A goose, clearly, at least in the breeding season. Geese nest on the ground, invest heavily in a small brood, and both parents defend it, so a nesting goose will readily hiss, spread its wings, charge, bite, and beat with the hard knob at the bend of the wing, and a large gander can knock a person over. Ducks are far less confrontational; a female with ducklings may feign injury to lead a threat away, or simply move off. Neither can seriously injure a healthy adult, and outside the breeding season both are wary and avoid people. The sensible response to a hissing goose is to give the nest a wide berth.

Rarely, and the offspring are usually infertile. Ducks and geese are different enough that hybrids between them are uncommon in the wild, though they do occur, and captive collections occasionally produce a mallard by greylag goose cross or similar. Within ducks, and within geese, hybridisation is much more frequent, since closely related species readily cross, which is one of the threats to the white-headed duck from the introduced ruddy duck, and a reason feral and domestic waterfowl can muddy the identification of wild birds on a park lake. A bird that looks like an odd mix of duck and goose features is far more often a domestic duck breed or a duck by duck hybrid than a true duck by goose cross.