Spatial and temporal variation in the Ecstatic Display Call of the Adélie penguin

Abstract

The Adélie penguin (Pygoscelis adeliae) is unique amongst penguins by having two distinct display calls, the mutual display (used for individual recognition) and the Ecstatic Display Call (EDC, used for mate choice and territory defence). Although there are low rates of migration in the Adélie penguin, no geographic variation has been found in the mutual display call. However, the potential for geographic variation in the EDC has not yet been studied in detail. The possibility that the EDC possesses geographic variation because of its duality of function and its freedom from the ties of recognition was investigated in three colony areas of Ross Island, Antarctica during two breeding seasons (2000/01 and 2002/03). The stability of the call was examined across breeding seasons, between colonies and concurrently with estimates of colony breeding success. Results indicated that some call parameters (pitch, Frequency Modulation, Amplitude Modulation, entropy and total call duration) varied between Ross Island colonies and that these parameters varied with both geographical location and colony size. In conjunction with variation in call parameters, the breeding success of the colonies was predictably different; larger colonies with better access to open water and potential foraging grounds had greater success and produced chicks in better condition. The call parameter differences from Cape Bird also indicated that the parameters that separate colonies altered between breeding years. The observed variation in call parameters may be akin to variation in breeding success. The EDC whilst retaining its individuality appears remarkably changeable, and with greater study (over longer time and with more disparate colonies) has the potential to be used as an indicator of climatic and colony condition.