learned vocalizations have been identified in groups including whales, elephants, seals, and primates, however the most well-established examples of learned singing is in birds. in many species, young birds learn songs from adult males of the same species, typically fathers. this was first demonstrated in chaffinches ("fringilla coelabs"). chaffinches raised in social isolation develop abnormal songs, however playing recordings of chaffinch songs allows the young birds to learn their species-specific songs. song learning generally involves a sensitive learning period in early life, during which young birds must be exposed to song from tutor animals in order to develop normal singing as adults. song learning occurs in two stages: the sensory phase and the sensorimotor phase. during the sensory phase, birds memorize the song of a tutor animal, forming a template representation of the species-specific song. the sensorimotor phase follows and may overlap with the sensory phase. during the sensorimotor phase, young birds initially produce variable, rambling versions of adult song, called subsong. as learning progresses, the subsong is replaced with a more refined version containing elements of adult song, called plastic song. finally, the song learning crystallizes into adult song. for song learning to occur properly, young birds must be able to hear and refine their vocal productions, and birds deafened before the development of subsong do not learn to produce normal adult song.