Hearing and communication in birds: the cocktail-party-effect in intraspecific communication of Agapornis roseicollis (aves, psittacidae).

Lovebirds ($\text{Agapornis roseicollis}$) were able to detect recorded acoustic signals of their mates from background noise (vocalizations of birds of the same species); signal-to-noise ratio 13 dB.Signal detection and intelligibility at different levels is so far known to be based on two components: The preferential motivation of the signal recipient as a psycho-physical factor, and - in the case of voice recognition in background noise - the possession of two ears as the physical factor. Since this complex phenomenon, termed the cocktail-party-effect, has first been investigated in the acoustic behaviour of humans (1,2), ethologists have supposed that this effect also exists in the animal acoustic behaviour of Vertebrates (3,4,5) and probably Invertebrates (pers. comm.).