Vocal labelling of family members in spectacled parrotlets, Forpus conspicillatus

Although there is increasing evidence that signalling animals can refer to objects external to themselves, only weak evidence exists that nonhuman animals use referential signals for different social companions. We tested whether spectacled parrotlets use different acoustic signals for different family members. We recorded two parrotlets interacting with one another during spatial but not visual separation. Discriminant function analysis of the acoustic cues of calls revealed high similarities between calls when both the individual and the interacting partner were loaded together as grouping variables. In playback experiments, the parrotlets were tested with contact calls of a family member recorded during interaction with the tested bird and with calls of the same stimulus bird recorded during interaction with another family member. The birds responded more often to calls uttered in their presence than to calls uttered in the presence of another family member. This suggests that spectacled parrotlets use contact calls to refer to a social companion and thus are labelling or naming their conspecifics. Spectacled parrotlets may thus have mental representations of their social companions, an important ability to live within their complex social system.