According to the Smithsonian Institution's "Birds of North America," Robins eat earthworms, insects and, in winter, berries and fruits make up the bulk of their diet. The American Robins, very common members of the thrush family (Bluebirds also are thrushes), can strip an American Holly of all its berries in one day. They did this every year to an enormous holly in our yard, and left evidence of their diet all over our cars. --Wendy