The structures of the avian outer and middle ears are furnished by the most extensive adaptive variations according to different ecological requirements. The cochlea with lagena is almost straight and cell arrangement in the cochlear duct is distinguished from the mammalian: Two types of hair cells lie in one continuous row, the cilia are inserted firmly into the tectorial membrane, the pattern of nerve innervation is quite different from that of the mammalian corti, and the orderly seqence of innervation on the basilar membrane is reserved obviously in tonotopical organization of the cochlear nuclei. Songbirds can hear most of the frequencies in their vocalization, while their ears are not the kind of specialization for communication seen in orthopterans and frogs: Recognition of conspecific songs involves in processing in the higher CNS rather than in the range of frequency alone. The behavioral relation of vocalization and hearing may light on tentative approaching the problem of pattern recognition in auditory CNS.