Ducks are mostly aquatic birds, mostly smaller than the swans and geese, and may be found in both fresh water and sea water.
Ducks eat a variety of food sources such as grasses, aquatic plants, fish, insects, small amphibians, worms, and small molluscs. Diving ducks and sea ducks forage deep underwater. To be able to submerge more easily, the diving ducks are heavier than dabbling ducks, and therefore have more difficulty taking off to fly.
The ducks are generally monogamous, although these bonds generally last a single year only. Larger species tend to have pair-bonds that last numerous years. Most duck species breed once a year, choosing to do so in favourable conditions (spring/summer). Ducks also tend to make a nest before breeding. Mother ducks are very caring and protective of their young although sometimes they will abandon some of their ducklings if they are physically stuck in an area they cannot get out of or are not prospering due to genetic defects or sickness brought about by hypothermia, starvation, or disease.
Ducklings can also be orphaned by inconsistent, late hatching where a few eggs hatch long after the mother has abandoned the nest.
Despite widespread misconceptions, only the females of most dabbling ducks “quack”. A common urban legend claims that duck quacks do not echo; however, this has been shown to be false. The ducks have a cosmopolitan distribution occurring across most of the world except for Antarctica. Worldwide, ducks have many predators. Ducklings are particularly vulnerable, since their inability to fly makes them easy prey not only for predatory birds but also large fish like pike, crocodilians, and other aquatic hunters, including fish-eating birds such as herons. Ducks’ nests are raided by land-based predators, and brooding females may be caught unaware on the nest by mammals, such as foxes, or large birds, such as hawks or eagles.
Adult ducks are fast fliers, but may be caught on the water by large aquatic predators including big fish such as pike. In flight, ducks are safe from all but a few predators such as humans and the Peregrine Falcon, which regularly uses its speed and strength to catch ducks.