Variation in call properties of the snow petrel, Pagodroma nivea, in relation to sex and body size

Abstract

We studied the physical parameters of calls of the snow petrel, Pagodroma nivea, in relation to body size, sex and individual specificity. Frequency parameters were related to body size in both males and females; larger individuals’ voices were pitched ≈2 kHz lower than those of smaller individuals. Males’ voices were pitched, on average, 376 Hz lower than those of females but the relation between frequency parameters and body size was similar in males and females. The rhythm of the call was sex-specific, the intersyllabic duration being shorter in females than in males. The variables most specific to individuals were those relating to frequency parameters, duration of the call and temporal patterning. The relationship between body size and frequency parameters, together with the high degree of geographic variation found in this species, suggest that care should be taken when analysing geographic variation in bird calls.