main idea. A. Male birds have a standard process for acquiring their songs that involves a sensitive period when learning takes place. B. Birds raised in the wild can differ from those raised in captivity in when they begin to sing their song, which is used to establish their territory. C. Testosterone levels in male birds affect the quality of the young bird's song. D. Birds that do not need to establish their territory, such as those raised in isolation, are unlikely to learn to sing. E. The learning of local dialects demonstrates that song acquisition involves both internal and environmental influences. F. Birds raised in the wild may acquire the songs of other species in their local area.