Communication value of displays and postures in Red-vented Bulbul Pycnonotus cafer (Aves: Pycnonotidae)

Abstract

I investigated visual signals mediated through displays and postures and their importance in communication in Red-vented Bulbul Pycnonotus cafer. Observations revealed that this species used five types (namely mate acquisition display, greeting display, alarm display, crest position and begging display) of visual signals for communication and showed three types of sleeping postures and broken-wing display. Mate acquisition display was performed to maintain pair bond and when two individuals met, one of them would use greeting display along with low amplitude complex vocalisations. The position of the crest seemed to vary with different behavioural contexts; it was raised erect in alarm and recumbent during greeting. Nestlings/ fledglings used specific begging displays that included gaping with or without vocal signals. The presence of a predator in close vicinity of bird/nesting site, elicited alarm displays along with alarm calls. The present study revealed that the displays and postures are important means of communication under various social contexts and were often accompanied with vocalisations thus making them multi-component. It is believed that the multi-component signals provide more reliable information for receivers and increase the efficacy of communication.