Abstract
Grey parrots are known for their ability to mimic human speech, which they can even use to categorize items, quantify arrays, or respond to queries concerning same-different and relative conjunctive concepts. Knowledge about their natural vocal communication is, however, relatively poor.
We studied repertoires and context specific vocalizations in 2 laboratory kept groups of African grey parrots. First, we recorded 3052 sounds of four wild-caught parrots, which were then categorized according to their characteristics using both visual inspection and listening into 70 different call types.
Subsequently, we verified the relevance of this categorization by cross-correlation. Our categories differed substantially from those previously identified by Giret et al. (2012).
Consequently, we exposed the same group of wild-caught parrots and a hand-reared group to different contexts (raptor, context of food, strange terrifying object, strange human and social isolation). One currently nesting wild-caught male and 2 birds from the hand-reared group reacted with a loud noisy call (probably a distress call) to predator.
Similar reactions were noticed in the context of strange terrifying object and in the presence of the strange human. In the context of food, members of the hand-reared group emitted specific vocalizations (high frequency peeps).
In the context of social isolation, a variety of calls were emitted by the hand-reared parrots, but tonal calls were more present than in neutral context. Also these context specific calls differ from the one determined by Giret et al. (2012).
Differences within groups can be caused by the fact that individual birds may experience different internal states in same contexts. Differences between independent social groups can be considered as evidence for the role of learning in repertoire structure.
Our result also seem to indicate that, contrary to most parrot species, grey parrots might not use specific alarm and contact calls.