A study of Choughs' vocal repertoire: variability related to individuals, sexes and ages

The calls uttered by Choughs (Pyrrhocorax pyrrhocorax) on Islay (S-W Scotla nd) were recorded during the breeding season. We analysed the vocal reperto ire and the degree of call variation, among and within individuals. Eight s tructurally different calls were identified in Choughs' vocal repertoire. S ignificant differences in temporal and frequency variables of calls were fo und between fledglings and adults, whereas females' and males' calls turned out to differ only in two parameters of the commonest call type ('chwee-ow '). Despite sex-related differences in this call, partners appeared to utte r similar versions of it, which suggests that male vocal mimicry might occu r. A certain degree of individuality, i.e. a greater among than within indi viduals variability, was found in three call types, but the reverse was fou nd in the commonest call of the species. Accordingly, we hypothesise that t his call might promote effective species recognition, whereas the other cal l types would be involved in individual recognition.