American robins may mob small predators, such as Cyanocitta cristata and Squamata. They also produce chirping and chucking sounds as warning calls.
Predators on young and adults differ somewhat. Eggs and young are often eaten by different types of Sciuridae, Squamata, and birds such as Cyanocitta cristata, Quiscalus quiscula, Corvus brachyrhynchos, and Corvus corax. Adult American robins are preyed upon by Accipitridae, Felis silvestris, and larger Squamata.
American robins are vigilant when feeding, they may feed in loose flocks, so that they can also watch other robins for reactions to predators. (Sallabanks and James, 1999)