The Red-winged Blackbird, Agelaius phoeniceus, is a passerine bird of the family Icteridae found in most of North and much of Central America. It breeds from Alaska and Newfoundland south to Florida, the Gulf of Mexico, Mexico and Guatemala, with isolated populations in western El Salvador, northwestern Honduras and northwestern Costa Rica. It may winter as far north as Pennsylvania and British Columbia, but northern populations are generally migratory, moving south to Mexico and the southern United States.
When displaying or in flight, the black adult male shows distinctive red shoulder patches. At rest, the male also shows a pale yellow wing bar. The female is blackish-brown with paler underside. Adult birds are 7 to 9.5 inches in length and weigh between 1.2 and 2.3 ounces; the female being smaller than the male. Young birds resemble the female, but are paler below and have beige feather tips. Both sexes have a sharp pointed bill.
The Red-winged Blackbird feeds primarily on plant seeds, including weeds and waste grain, but about a quarter of its diet consists of insects, spiders, mollusks and other small animals. In season, it eats blueberries, blackberries, and other fruit. These birds can be lured to backyard bird feeders by bread and seed mixtures.
During the breeding season, males will arrive to the respective location a few days before the females. Once there, the male stakes out its territory by singing. They defend their territory aggressively against other male Red-winged Blackbirds and against birds they perceive as threatening. They will even defend their area from human intrusion. The territorial male will defend up to ten females. However, females frequently copulate with males other than their social mate and often lay clutches from mixed mates.
Red-winged Blackbirds prefer marshes, but will nest near any body of water. Pairs raise two or three clutches per season, in a new nest for each clutch. The nests are cups of vegetation, and are either built in shrubs or attached to marsh grass. A clutch comprises three to five eggs. These are incubated by the female and hatch in 11-12 days. Red-winged Blackbirds are ready to leave the nest ten days after hatching.
When the breeding season is over, Red-winged Blackbirds gather in huge flocks, sometimes numbering in the millions. In some parts of the
United States, they are considered to be pests because these flocks can consume large amounts of cultivated grain or rice.