Ducks are not very picky when it comes to their food; they just usually exploit the different food sources they can find around them, such as weeds, small aquatic plants, fishes, insects, slugs, and even snails.
Some breeds of ducks such as the smew, goosander and the ganders, are well-adapted to hunt and eat large fish.
Most ducks have the feature of a wide, flat bill that helps them in scouring for food, pulling plants, catching worms and small snails from the ground, hunting for small insects and other jobs such as grooming and defending themselves from predators.
Diving ducks and sea ducks hunt deep underwater. To submerge easily, the diving ducks are built heavier than the dabbling ducks, and they also have more difficulty in flying.
Dabbling ducks on the other hand feed on the surface of the water or on the shore, or as deep as they can submerge their bodies. On the side of the bill, there is a specialized structure, resembling a comb with fine bristles, used to strain the water spurting from the side of the bill and traps the food. This is called the pectin, which is also used to clean the feathers.
Ducks are basically monogamous, even though these bonds generally last for a specific period only such as a year or a season. Larger breeds and the more docile breeds are inclined to have a single partner for a longer time. Most breeds copulate at least once a year, during a certain favorable situations depending on the region they live.
Despite the popular notion, only the female ducks of most dabbling varieties quack. For instance, the scaup, a diving duck, makes a noise that makes a sound like scaup (thus the origin of the name), and even among the dabblers, the males do not quack. Generally, ducks make a wide range of sounds or calls varying from whistles, and grunts. These sounds, also known as calls, may be loud displaying calls or subtle communication during the mating season.
Ducks have a broad-based distribution, occurring across most of the regions of the world, except in arid regions like Antarctica, and in most deserts. Most species can thrive in sub-Antarctic areas such as South Georgia and the Aucklands. Most ducks have also thrived to inhabit on oceanic islands such as New Zealand and the Hawaiian Islands, even though most of these species are endangered or have been declared as extinct.
A few duck species, primarily those breeding in the moderate climate regions are very migratory; those in the tropics are not. Some ducks, especially in Australia and New Zealand are nomadic because of the rainy season.
Ducks have different predators to look out for. Ducklings are very vulnerable since they cannot fly or run fast and they are basically food for large birds and large fishes such as pikes, and other aquatic predators such as crocodiles. The coop can be raided by land predators, and brooding ducks may be trapped on the nest by foxes, or predatory birds such as eagles and hawks.
Mature ducks can fly, but can be trapped on the water by large predators such as large fishes. In flight, ducks are safe from a few predators except from humans and hawks.