One of the commonest birds in North America, and a most boldly colored one, the Red-winged blackbird is often seen on cattails, on telephone wires and along boggy roadsides. The males are glossy-black with shoulder patches of scarlet and yellow which they are able to puff up or hide according to their level of confidence. Females look like a big, dark sparrow, being a subdued, streaky brown. In the north, the early arrival and tumbling song of these birds are welcome indications of spring's return.
This species inhabits Canada, south-eastern Alaska, the United States as far as the Gulf Coast, and is also found in Central America and in the northern Caribbean islands. Populations that are most northerly migrate south after the mating season, but some of the populations in the central and western United States, Central America and the Gulf Coast are resident year-round. In the breeding season, Red-winged blackbirds are found in a range of fresh and saltwater environments, including in small trees and bushes along marshes and watercourses, in agricultural areas and dry meadows. During migration, they can be found in, pastures, prairies and cultivated fields.
As a migratory bird, a Red-winged blackbird is a strong flier that often will join a flock of more than a thousand to migrate. This species is largely diurnal, and throughout the year spends most of its day foraging and gathering into roosts. In summer months these birds congregate in wetland areas where they breed, but in winter they may roost with other birds, such groups being sometimes a few individuals or up to several million. Every morning the roosts disperse, travelling up to 50 miles to feed, then re-forming at night. These birds are active feeders, using their strong bill to open up the leaf bases of reeds and aquatic plants, or lifting sticks and stones to find hidden insects. They also eat seeds and other items off the ground and will glean insects from vegetation. They are strong fliers, with an up and down pattern of flight.
Red-winged blackbirds are omnivores, they mainly eat seeds, but they also feed on insects, spiders, mollusks, worms, snails, mussels, crayfish, frogs, lizards, nestlings, birds' eggs, fruit and berries.
Males are polygynous and will mate with several females nesting inside their territory. Some populations see 90% of territorial males with more than one female blackbird nesting in their territory. However, females may also have multiple partners, and one-quarter of the nestlings may be fathered by different males. This means that females exhibit polyandrous mating system. Prior to breeding, a male does everything he can to get noticed, perching up high, all day long singing his “conk-la-ree” song. Males may chase females with their shoulder feathers erect. Breeding starts in early spring and goes until mid-summer. These birds nest within crowded groups, low down among the vertical shoots of vegetation in the marshes, shrubs, or trees. The female builds the cup-shaped nest and lays 3 to 7 eggs of pale blue green spotted with purple and dark brown. Incubation is by the female alone and lasts around 11 to 13 days. The young are altricial and at 11 to 14 days old they leave the nest, but remain within the territory for two more weeks. The female feeds them, sometimes helped by the male, for as long as 3 more weeks after they have left the nest territory.
As one of North America's most common and numerous birds, not much effort is put into protecting Red-winged blackbirds from the impact of urbanization and habitat loss. Because they are able to survive in a wide range of habitats, many populations are able to cope with losses of natural terrain. However, these birds thrive in wetland areas, so with the loss of such areas they are likely to be affected.
According to the IUCN Red List, the total Red-winged blackbird population size is 210 million mature individuals. According to the All About Birds resource, the total breeding population size of the species is 130 million individuals. Overall, currently Red-winged blackbirds are classified as Least Concern (LC), but their numbers today are decreasing.
As highly generalized foragers and predators, Red-winged blackbirds control insect populations through predation and weed populations through the consumption of seeds.