The tree swallow (Tachycineta bicolor) is a migratory bird of the family Hirundinidae. Found in the Americas, the tree swallow was first described in 1807 by French ornithologist Louis Vieillot as Hirundo bicolor. It has since been moved to its current genus, Tachycineta, within which its phylogenetic placement is debated. The tree swallow has glossy blue-green upperparts, with the exception of the blackish wings and tail, and white underparts.
Description: The tree swallow has a length between about 12 and 14 cm (4.7 and 5.5 in) and a weight of approximately 17 to 25.5 g (0.60 to 0.90 oz). Wingspan ranges from 30 to 35 cm (12 to 14 in).The male has mostly glossy blue-green upperparts, the wings and tail being blackish. The underparts and the cheek patch are white, although the underwing coverts are grey-brown.The bill is black, the eyes dark brown, and the legs and feet pale brown.The female is duller in colour than the male, and sometimes has a brown forehead.The second-year female also has brown upperparts, with a variable number of blue feathers; some third-year females also retain a portion of this subadult plumage.
Distribution and habitat: The tree swallow breeds in North America. Its range extends to north-central Alaska and up to the tree line in Canada. It is found as far south as Tennessee in the eastern part of its range, California and New Mexico in the west, and Kansas in the centre. It occasionally breeds further south in the US and vagrants are sometimes found in the Arctic Circle, the northern Pacific, Greenland, and Europe.
The wintering range is from California and southwestern Arizona in the west and southeastern Virginia in the east south along the Gulf Coast to the West Indies, Panama, and the northwestern South American coast.While migrating, this swallow often uses stop-over sites, spending an average of 57 days at these areas during autumn. To get to its wintering range, it often uses one of three flyways: the Western flyway, west of the Rocky Mountains; the Central flyway, between the Rocky Mountains and the Great Lakes, stretching south into Eastern Mexico; and the Eastern flyway, from the Great Lakes east.
Behaviour: Because of the large amount of research on the tree swallow and how it willingly breeds in nest boxes, biologist Jason Jones recommended that it be considered a model organism. Although it is aggressive during the breeding season, this swallow is sociable outside of it, forming flocks sometimes numbering thousands of birds.
Breeding: The tree swallow nests in structures with pre-existing holes, both natural and artificial. These were once found only in forested regions, but the building of nest boxes has allowed this bird to expand into open habitats.This swallow usually nests in the area it bred the year before; only about 14% of females and 4% of males disperse to breed at a new site per year. Most do not go far, usually breeding at sites less than 10 kilometres (6.2 mi) away from their original grounds.
Feeding: The tree swallow forages up to 50 metres (160 ft) above the ground singly or in groups. Its flight is a mix of flapping and gliding. During the breeding season, this is mostly within 4 kilometres (2.5 mi) of the nest site. When it is foraging for nestlings, though, it usually goes up to 200 metres (660 ft) from the nest, mostly staying in sight of it, and forages at a height up to 12 metres (39 ft).As well as being caught in flight,insects are sometimes taken from the ground, water, vegetation, and vertical surfaces
Status: The tree swallow is considered to be least concern by the International Union for Conservation of Nature. This is due to the bird’s large range of about 834,000 km2 and its stable population, estimated to be about 20,000,000 individuals It is protected in the US by the Migratory Bird Treaty Act, and in Canada by the Migratory Birds Convention Act.
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