The avian cochlea is the principal model for the investigation of hair-cell regeneration and the recovery of function in the vertebrate auditory periphery [1]. This capacity for repair in birds would seem to preclude permanent sensorineural hearing loss involving hair cells, which is the most common cause of hearing disabilities in humans [2]. Here, we report the first evidence of a permanent sensorineural hearing loss in a bird. This loss is due to missing and abnormal hair cells and consequent physiological malfunction of the cochlea. Belgian Waterslager canaries have been bred for nearly 100 years for specific song characteristics and their contact calls are especially low pitched. Very early reports indicate that a high proportion of these birds produced faulty song compared to German canary strains [3]. Since canaries learn their songs from an external model and also relv on auditory