Robins are Birds of a feather, but color is what separates sexes American robin is the name sanctioned by the American Ornithologists' Union, as there are other birds of different species in the world also named robin. An observer can tell robin sexes apart since the female robin has a paler back and breast and no black head.
Robins are primarily monogamous and are normally devoted to only one mate at a time.
They usually rear two or three broods in spring and summer, and almost always remain with the same mate for successive broods within a nesting season. They probably don't mate for life because of scattering during migration. Also, males arrive about five weeks before females sexes return to their previous northern territories each spring, there is a chance of successive remating. One observer reported that a robin built her nest five consecutive years in a woodbine vine trailing up a porch. The robin was identified by a white mark on the side of her head.