Waterfowl are any of more than 150 different species of water birds that belong to the taxonomic Order Anseriformes. They include the ducks, geese, swans, screamers, and other relatives. They are characterized by their flat bill and webbed feet.  Waterfowl live in all parts of the world, and most have the ability to fly as well.
Waterfowl can weigh from 2 lbs. to 48 lbs. They have long necks, wings, a bill (or beak), and feathers. Its bill is in two different parts. The top mandible is an extension of the skull and so it cannot move. The lower mandible does all the moving and chewing. They do not have teeth for chewing, instead they have lamellae made out of a hard material of the mandible. 
Different Waterfowl have various types of feet depending on their mode of transportation such as walking or swimming. Swimmers will have flat foot bones to reduce resistance in the water, and their hind toe is lobed (has a roundish projection or division). Webs are also fully developed between the toes of most anseriformes. 
Like the feet, the wings vary between different anseriforms from broad wings for slow fliers to narrow, speedy wings. The screamers are still the only kind of anseriformes able to soar. Some whistling ducks have modified vanes on their wings that make a whirring sound when they fly.
The color of their plummage depends on several factors including what season it is, sex and maturity. Some species have brightly-colored patches on their feathers while others have a single color.
Reproduction in waterfowl typically happens isolated in water. It is not normal for anseriformes to breed in colonies. If there ever is colonial breeding, their nests are usually distances apart. Screamers (family: anhimidae) make their nests out of weeds and sticks close to the water. They will return to the same nest for many seasons if not their whole life. Both sexes build and defend the nest. They will lay 2-7 eggs at a time and the parents will take turns incubating, warming, and guarding for up to 45 days. 
Some species of waterfowl make their nests close to the water, others may build their nests miles away from the water. They can build their nests either on the ground or in trees. Nests are usually made of anything they can find. Only shortly before the eggs are to be lain, the female will line the nest with down feathers plucked from their underside. The number of eggs lain can vary greatly from 2-22 eggs at a time. The female incubates, warms, and guards eggs from 22-40 days depending mainly on the species. Males have no active part in this in most species.
When a chick has finally hatched, it has a down covering that is not yet water repellent. It gains this by rubbing against the mother's feathers again and again. Ducklings feed independently from the very first day. Ducks will care for their young until they are able to fly, which takes between 40-70 days. Geese and swans will care for their young until the following spring.
Most anseriformes are very active during the day and take shelter at night. They are very social when they're not nesting. During winter, they will gather in groups of up to 3000 at a time. Anseriforms live in aquatic habitats such as lakes, rivers, swamps, ponds, and streams. Most waterfowl are in fresh water rather than salt water (at least during breeding season). Only few will inhabit deep lakes or fast streams. They prefer rich, shallow water that has been glaciated (frozen or freezing) such as deltas of rivers, marshes, or shallow lakes. You will probably find more ducks in small patches of water than in a huge lake because the shore is very important for breeding pairs, food, cover, and protection. Anseriforms are threatened by owls, crows, skuas, skunks, raccoons, fox, coyotes, and humans. Anseriformes mainly eat plants: flowers, leaves, and roots, but occasionally they will eat small sea creatures like mollusks or fish and a few insects. 
In 1980, there was a drought in Canada that almost caused the Canadian geese to become non-existent. A recent wet cycle enabled a large population increase. Its population has grown to about 1 million with a growth rate of 14% a year. This brought great effects on crops. Farmers protested and law was made so that they can kill a certain number of Canada geese outside of the fall season. 
Another species that is becoming overpopulated is the snow goose. In 1965 there were only about 30,000 snow geese. That has increased to about 1 million and is still increasing at about 9% rate of growth each year. They eat plants and "grub" roots before they sprout. This causes the marshes to become exposed to erosion. They are also affecting farmers crops. Attempts to harvest more snow geese have failed. Now refuge managers plan to harvest them at their arctic breeding grounds.
- geese overpopulation
- Canadian geese overpopulation