Parting self from others: Individual and self-recognition in birds.

Individual recognition is the ability to differentiate between conspecifics based on their individual features. It forms the basis of many complex communicative and social behaviours. Here, we review studies investigating individual recognition in the auditory and visual domain in birds. It is well established that auditory signals are used by many birds to discriminate conspecifics. In songbirds, the neuronal structures underpinning auditory recognition are associated with the song system. Individual recognition in the visual domain has mainly been explored in chickens and pigeons, and is less well understood. Currently it is unknown which visual cues birds use to identify conspecifics, and whether they have cortical areas dedicated to processing individual features. Moreover, whether birds can recognise themselves visually, as evidenced by mirror self-recognition, remains controversial. In the auditory domain, the responses of neurons in the song system suggest identification of the bird's own song. The surveyed behavioural and neural findings can provide a framework for more controlled investigations of individual recognition in birds and other species.