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Dialects in ravens Corvus corax; new aspects of an old problem [abstract]

Peter Enggist (1997). Dialects in ravens Corvus corax; new aspects of an old problem [abstract]. Bioacoustics, Volume 8 (3-4): 255



Several studies have shown that male songbirds react differently to songs of their own, adjacent and foreign dialects. Because reactions to neighbour's and stranger's song of the same dialect were not compared, and because it was not controlled for structural similarities among the tested songs, the interpretation of the differences in reaction remains difficult. It might be that discrimination between alien and foreign dialects is not principally different from the well known discrimination between songs of neighbours and strangers, but might be explained by reacting to differences in structural similarity between the songs. Therefore Falls (1982) speculated that neighbour-stranger discrimination would be weak compared to the discrimination between dialects because dialects are more differing in structure than the vocalisations of neighbours of the same dialect. We tested this hypothesis on ravens' Corvus corax male repetitive calls. Detailed analysis of the vocal repertoire of 37 resident pairs and the geographic distributions of the call types showed that two repetitive call types of males and two of females divided the study area into two dialect regions. Playback experiments were conducted on males of one of the dialect regions. They reacted differently to neighbours' and strangers' calls of the same dialect, but not differently to calls of the adjacent dialect. Whereas calls of the two dialects are clearly structurally different, neighbours' and strangers' calls within the same dialect do not differ in structural similarity. These results indicate that there is not a tight relationship between signal structure and meaning in the sense that the more differing the signals, the more differing also the reactions, as has been assumed so far. To interpret our results and to advance our understanding of communication in general, we propose a shift in the point of view from looking at signals and at the reactions to them as properties of individuals alone to one considering them as elements of a relationship between individuals.