REGIONAL DIALECTS IN THE CONTACT CALL OF A PARROT

This study describes a system of regional dialects in the contact call of a parrot, the yellow-naped amazon (Amazona auropalliata). Spectrog raphic cross-correlation analyses of calls from multiple adults at 16 roosts in Costa Rica reveal two distinct patterns of geographic variat ion in call structure: first, variation in the basic structure of the call by which roosts can be classified into three distinct dialects, a nd second, fine-scale variation of call structure among roosts within a dialect. Some birds at roosts bordering two dialects use the calls o f both neighbouring dialects interchangeably. These results suggest th at there are two distinct processes governing the diffusion of call ty pes among roosts, with dialect borders acting as barriers to the sprea d of foreign calls. Such a dialect system could be maintained through either reduced dispersal of birds across dialect boundaries or alterna tively, by reduced diffusion of call types. These two possibilities ha ve different implications for the genetic isolation of populations and thus for both speciation and learning. This pattern is broadly simila r to those seen in some songbirds and may be maintained in a similar m anner.