A spectrographic analysis of the loud calls of Helmeted Hornbills Rhinoplax vigil

Abstract

Helmeted Hornbills Rhinoplax vigil inhabit the tropical and montane forests of Borneo, Sumatra, Malaysia, and Peninsular Thailand. Although little is known of their social behaviour and ecology, it is believed that they are monogamous and strictly territorial. The males have been observed to produce loud calls audible up to 2–3 km at various times throughout the day, but no studies of these calls have been made previously. An audiospectrographic analysis of the loud calls produced by several wild Helmeted Hornbills was conducted. The sounds comprising the loud calls were relatively pure in tone with few harmonics, with most of the energy produced between 500–1500 Hz, suggesting that selection may have favoured the long‐range transmission of these sounds through the forest. These calls are organized into two distinguishable parts, and it is suggested that the first part may primarily serve as a means of attracting the attention of neighbouring non‐mate conspecifics, while the second part may serve as an advertisement of age, size, or physical condition.