Foraging primarily in areas of shallow water or on mudflats, the blue-winged teal feeds on seeds, roots, grass, sedge, algae and other aquatic plants, as well as insects and aquatic invertebrates, such as molluscs and small crustaceans (2) (3) (7). Before egg-laying, the female blue-winged teal consumes large amounts of invertebrates, mostly insect larvae and snails, to provide enough energy for egg production and incubation (3). The blue-winged teal rarely dives fully below the surface, instead feeding mainly by dabbling on the surface with just the bill submerged, or by dipping just the head under the water. It will also glean invertebrates from submerged or floating vegetation (2) (3) (6).
Like other small dabbling ducks that breed in North America, the blue-winged teal forms pairs in late winter, or during the northern migration in spring (3) (6). Breeding typically begins in May (2). The female selects a territory on arrival at the breeding grounds, which is defended by the male during breeding (3). The female builds the nest just before the first egg is laid, typically selecting a well-hidden site in upland vegetation and using the feet to scrape a bowl-shaped depression in the ground. The nest is then lined with grasses found around the nest site, as well as with down and feathers (2) (3) (6).
Generally, the female will lay 10 to 12 eggs, although clutch size ranges between 6 and 15 eggs (2) (3) (7), which are incubated for 21 to 27 days (2) (7). The ducklings spend very little time in the nest, typically less than 24 hours, before making their first journey to water (3) (7). The female broods the young, although the male blue-winged teal may occasionally accompany young broods for short periods (3). The young are able to feed with out assistance from the adults, but the female remains with the ducklings for around two weeks, leading the young to appropriate feeding sites. The young blue-winged teals fledge at around 35 to 44 days old (2) (3) (6) (7).
The male blue-winged teal leaves the breeding grounds before the female, moving to suitable moulting cover among thick vegetation, where it becomes flightless for a period of three to four weeks (7). The blue-winged teal migrates to its wintering habitats much earlier than similar species, typically departing around mid-August. The male leaves first, with the female and juveniles following by mid-September (3) (7). The blue-winged teal migrates in small flocks that display strange flight patterns composed of quick twists and turns carried out in unison (6).