PREDATION OF A PACIFIC TREE FROG (PSEUDACRIS REGILLA) BY AN AMERICAN ROBIN (TURDUS MIGRATORIUS) ON SAN JUAN ISLAND, WASHINGTON

Abstract The diet of the American Robin (Turdus migratorius) consists largely of fruit and invertebrates. Rarely, predation of small vertebrates has also been reported, including attacks on, and/or consumption of, snakes, a skink, fish, shrews, a field mouse, a salamander, and frogs. Few observations have included a prolonged interaction, leaving unanswered questions about how the prey are subdued, killed, and eaten. Here I describe an 8-min encounter between an adult male Robin and a Pacific Tree Frog (Psuedacris regilla), including plausible prey-dropping, pursuit, bill-pouncing, pecking, and beating the frog against the ground. The frog was killed, but not consumed, apparently because it was too large to swallow whole and the Robin failed to open or dismember the carcass. This marks the first reported attack by a Robin on a Pacific Tree Frog, and the first confirmed Robin kill of any frog species.