Laiolo P. & Rolando A. (2002) The begging call of the Red-billed Chough Pyrrhocorax pyrrhocorax: An analysis of its spectrotemporal variability. ARDEA 90 (1): 139-147

We analysed the spectrotemporal features of the begging calls of Red-billed Chough Pyrrhocorax pyrrhocorax females in five localities (Scotland, Western Alps, Central Apennines, Sicily and Morocco), focusing on variation at three different levels: within individuals, within populations and among populations. We analysed the relationship between the spectral features of the call and body size of the populations, the latter obtained from measurements on museum specimens. As the frequency of the first band of the call exhibited a great constancy within population, we hypothesise that it might be a population specific feature, affected and constrained by body size. In fact, the largest-bodied populations uttered calls with the lowest pitch, thus supporting the reverse correlation between body size and call frequency, already demonstrated in the trill call of the species. Conversely, the frequency band carrying most energy seemed to vary irrespective of body size, exhibiting a great variability at all analysis levels. Call duration, despite its high variability, appeared to characterise both individuals and populations. Comparison with a previous study carried out on the trill call suggests that the pattern of geographic differentiation of the two calls is not entirely matching. We re-analysed part of the trill call data to assess if the forces driving the evolution of the spectrotemporal features differently act (or have acted) on the two call types