The Northern Mockingbird, Mimus
polyglottos, is an imitator, singing the songs of many other birds,
repeating each three times. This pattern of three easily
distinguishes the Mockingbird from the Catbird, with no repeat, and the
Brown Tshrasher, with two repeats. This bird feeding on Sumac is
in the John Heinz National Wildlife Refuge near Philadelphia, PA.