Distress call in six species of African Poicephalus parrots

Abstract

We report here a description of the bioacoustic structure of distress calls of a number of African parrots, namely six species pertaining to the genus Poicephalus. The description is based on an analysis of 1523 distress vocalizations, totalling 8.54 min of record. The Poicephalus distress calls sound like a threatening growl that is composed of a series of short harmonic, scarcely modulated pulses, one following another in a short time. To be efficient over long distances and to be easily located by all possible receivers, the basic acoustic shape of this call showed a complex carrier frequency, numerous harmonics, low frequency modulation and wide frequency range. The highest frequencies of distress call emitted by African Poicephalus parrots exceeded 10 kHz; high frequencies are greatly attenuated with distance so that the distress call may efficiently provide information on both long distances and also on short ones. The degradation of high frequencies may be used by the receiver to determine the emitter distance or to startle mammal predators into releasing the distressed parrot. The distress call of African Poicephalus parrots is also a sexually dimorphic vocalization, with significant differences in the main physical parameters of the two sexes of all the species studied. Finally, we found significantly differences between species and superspecies even though the vocalization is extremely conservative.