Robins are large thrushes, 9-11" in length. They are brown above, reddish on the breast, and white on the lower belly and undertail feathers. Their throats are white, streaked with black. Females are slightly duller and paler in color than males. Young juveniles have dark spots on their breasts and are also paler in color than the adult males.
American Robins feed on a mixture of both wild and cultivated fruits, berries, earthworms, and insects such as beetle grubs, caterpillars, and grasshoppers. The Robin is flexible and will turn to whichever food is most readily accessible, although the diet generally consists of approximately 40% invertebrates, 60% fruits and berries.
Breeds in the spring shortly after returning from the migration to their more northerly habitat. Breeding season is from April through July. The Robin is one of the first birds to begin laying eggs and normally has two or three broods. The cup-shaped nest is built by the female, who builds the outer foundation with long coarse grass, twigs, paper and feathers woven together. She lines the inner bowl with mud, smearing it with her breast and later adding fine grass or other soft material to cushion her eggs. The nest is located on the ground or high up in trees, but most commonly 5 to 15 feet above ground in a dense bush, in the crotch of trees, on on window ledges or other human structures. All that is needed for the nest is a firm support and overhead protection from rain. In northern areas, the first brood is generally raised in a coniferous evergreen tree or shrub, and the later one or two broods in a deciduous tree. Usually three to five blue-green eggs are laid and incubated by the female for a period of about 14 days. She continues brooding the chicks while they are very young, then later doing so only during bad weather and at night. The male assists only by collecting material for the nest and sometimes feeding the chicks.
The Robin is migratory, and during migration robins assemble in large flocks established at night roosts, often in a secluded swamp. These roosts can become quite enormous in the southern part of the robin's range, breaking up to feed in small flocks on fruits and berries. There is much rivalry between the males, especially during the breeding season. The robin uses its voice as its main form of communication. It produces a variety of sounds, some loud and piercing that signify alarm, others high-pitched hissing sounds associated with scolding, call notes and a melodic song.