Temporal and Spectral Analyses Reveal Individual Variation in a Non-Vocal Acoustic Display: The Drumming Display of the Ruffed Grouse (Bonasa umbellus, L.)

摘要

Individual variation in vocalizations is a common feature of many forms of long-distance communication in vertebrates. The extent to which individual variation occurs in non-vocal, long-distance acoustic communication has not, however, been tested. Here, we examine the spectral and temporal characteristics of a non-vocal acoustic signal, the wing-beating drumming display of the male Ruffed Grouse (Bonasa umbellus, L.), and test whether its structure varies more among individuals than within them. Drumming displays were recorded over two field seasons, and we measured several temporal and spectral features of these recordings. Each drumming display consists of 3950 pulses produced over a period of 910 s with most of the energy concentrated at frequencies below 100 Hz. We calculated the potential for individual coding of several temporal and spectral features, and both the number of pulses and pulse rate were highly individually specific. This was corroborated by analyses of variance, bivariate plots of pulse number and rate, and discriminant function analyses. Overall, we conclude that male Ruffed Grouse produce individually specific drumming displays in a similar fashion to vocal individuality in other birds. The extent to which these individual differences persist from one season to the next is unclear, but individual differences in the number of pulses and pulse rate could provide information on individual identity to conspecifics.