duck

The ducks have a cosmopolitan distribution occurring across most of the world except for Antarctica. A number of species manage to live on sub-Antarctic islands like South Georgia and the Auckland Islands. Numerous ducks have managed to establish themselves on oceanic islands such as Hawaii, New Zealand and Kerguelen, although many of these species and populations are threatened or have become extinct.

Mallards on ice-covered pool in Hannover, Germany
Some duck species, mainly those breeding in the temperate and Arctic Northern Hemisphere, are migratory; those in the tropics, however, are generally not. Some ducks, particularly in Australia where rainfall is patchy and erratic, are nomadic, seeking out the temporary lakes and pools that form after localised heavy rain.[citation needed]

Ducks have become an accepted presence in populated areas. Migration patterns have changed such that many species remain in an area during the winter months. In spring and early summer ducks sometimes influence human activity through their nesting; sometimes a duck pair nests well away from water, needing a long trek to water for the hatchlings: this sometimes causes an urgent wildlife rescue operation (e.g. by the RSPCA) if the duck nested somewhere unsuitable like in a small enclosed courtyard.