Chickadees and titmice are mainly small stocky woodland species with short stout bills. Smaller birds such as robins, black capped chickadees, and sparrows are also present. Other birds, such as chickadees, cardinals, blue jays, and woodpeckers, live on the island year-round. In North America, chickadees, nuthatches, woodpeckers, purple martins and other swallows may be affected. Smaller birds (robins, jays, grosbeaks, chickadees, and so on) also abound. Chickadees, white-tailed deer, and eastern gray squirrels can be seen quite often. During the winter, chickadees often flock together. The Junior Chickadees, who serve as The Junior Woodchucks' female counterparts. One example from 1974, noted the competitive behaviour between mountain chickadees and violet-green swallows. It appears to be more rare, but interbreeding with boreal chickadees has also been documented. When flocking, black-capped chickadees soon establish a rigid social hierarchy. American species in this genus are known as chickadees. Black-capped chickadees, living in temperate forests of North America, do not migrate south during winter. Black-capped chickadees may interbreed with Carolina chickadees or mountain chickadees where their ranges overlap. Sawfly larvae formed 43% of the diet of chestnut-backed chickadees ("Poecile rufescens").