Habitat
The Green-winged Teal lives in shallow wetlands, preferring fresh water for breeding, but is resident on both fresh and salt water at other times of the year. Nesting habitat usually has trees and shrubs. During winter and migration, wetlands with a lot of emergent and floating vegetation are commonly used. Tidal mudflats are used by this species more often than by any other duck.
Behavior
Green-winged Teals usually gather in smallish flocks, but large flocks of thousands are also seen. Active and agile, they forage in emergent vegetation along shorelines and in wet, shallow, muddy areas, mainly by dabbling their bills at the water's surface. Because of their small size and rapid wing-beats, these birds in flight appear to move very fast.
Diet
The Green-winged Teal's diet is variable depending on season and location, with more animal matter consumed during the spring and summer, and more plants eaten in the fall and winter. Plant matter usually consists of the seeds of grasses, sedges, and pond-weeds. Animal matter is most often insect larvae, other aquatic invertebrates, and sometimes fish eggs.
Nesting
Green-winged Teals usually arrive at the breeding grounds with pair bonds formed. Nests are usually located in grasses and weeds in meadows, open woodlands, or brush, and are usually within two hundred feet of water. The female builds the nest on the ground. It is well hidden by low vegetation that often is dense enough to form a full canopy over the nest. The nest itself is usually a shallow depression, filled with grasses, twigs, and leaves, lined with down. Incubation is by the female alone, and lasts for 20 to 24 days, during which time the pair bond dissolves, and the male leaves the nesting area. Within a few hours of hatching, the 8 to 9 ducklings leave the nest with the female to look for their own food. They may all return to the nest at night for a few days. The young fledge at about 35 days.
Migration Status
Nearly all populations of Green-winged Teal are migratory, although they remain farther north during the winter than other species of North American teal. After incubation begins, the males migrate to molting grounds where they gather and go through a period of flightlessness. The molt migration may be to a spot close by, or may be over one hundred miles away. Fall migration occurs over an extended period, beginning in late August and stretching into early December. Females may move farther south than males. Spring migration usually begins in February and lasts through April. They often migrate over the ocean, sometimes in association with sea ducks.
Conservation Status
With 80% of the North American Green-winged Teal population breeding north of the United States-Canada border, most of the breeding grounds are away from human activity, and thus numbers have remained fairly stable and are even increasing in some areas. In 1990 the population was estimated at over 3,000,000 birds. The Common Teal, or Eurasian Green-winged Teal, a Eurasian subspecies of the Green-winged Teal, is recorded in small numbers in Washington in most years, and sightings have become more common, especially in the late winter and early spring. The increase in sightings may be due to an increase in birds, or an increase in reporting rates due to more birders out there looking for them. The Common Teal is currently considered the same species (although a different subspecies) as the Green-winged Teal in North America. However, British ornithologists recently split the two into different species, and some speculate that the American Ornithologists Union will soon follow their lead.