From 3 to 5 smooth, glossy blue eggs are incubated by the female and hatch in about two weeks. Young are born naked and blind. They are tended by both parents, and leave the nest in about 14 to 16 days. It takes about a month for the young birds to learn to feed themselves. The underside of the adult bird is brick red.
Young birds are more mottled.
The red color elicits a strong aggressive response during the breeding season. Many robins will spend hours and days attacking their reflection in a window or a shiny surface on a car. Primary flight feathers are grayish. Wingspan is 14 to 16 inches. The tail feathers are blackish and show a white spot on each outer tail feather.