The nominate subspecies of the American Robin is 23 to 28 cm (9.1 to 11 in) long with a wingspan ranging from 31 to 41 cm (12 to 16 in), with similar size ranges across all races. The species averages about 77 g (2.7 oz) in weight, with males ranging from 72 to 94 g (2.5 to 3.3 oz) and females ranging from 59 to 91 g (2.1 to 3.2 oz).Among standard measurements, the wing chord is 11.5 to 14.5 cm (4.5 to 5.7 in), the culmen is 1.8 to 2.2 cm (0.71 to 0.87 in) and the tarsus is 2.9 to 3.3 cm (1.1 to 1.3 in).[The head varies from jet black to gray, with white eye arcs and white supercilia.The throat is white with black streaks, and the belly and undertail coverts are white. The Robin has a brown back and a reddish-orange breast, varying from a rich red maroon to peachy orange.The bill is mainly yellow with a variably dark tip, the dusky area becoming more extensive in winter, and the legs and feet are brown.
The sexes are similar, but the female tends to be duller than the male, with a brown tint to the head, brown upperparts and less bright underparts. However, some birds cannot be safely sexed on plumage alone.The juvenile is paler in color than the adult male and has dark spots on its breast,and whitish wing coverts.First-year birds are not easily distinguishable from adults, but they tend to be duller, and a small percentage retains a few juvenile wing coverts or other feathers.
Data refer: http://en.wikipedia.org/wiki/American_Robin
The sexes are similar, but the female tends to be duller than the male, with a brown tint to the head, brown upperparts and less bright underparts. However, some birds cannot be safely sexed on plumage alone.The juvenile is paler in color than the adult male and has dark spots on its breast,and whitish wing coverts.First-year birds are not easily distinguishable from adults, but they tend to be duller, and a small percentage retains a few juvenile wing coverts or other feathers.
Data refer: http://en.wikipedia.org/wiki/American_Robin
