Study of altitudinal and geographical song variation and interspecific interaction among Phylloscopus warblers in the Himalayas.

Abstract

Sound is predominant mode of communication among birds and has advantages over visual communication, particularly where habitats are dense. Bird vocalizations are usually categorized into calls and songs. The study is based on geographical song variation in two leaf warblers i.e. Grey-hooded Warbler, Phylloscopus xanthoschistos and Blyth’s Leaf Warbler Phylloscopus v reguloides. These species occur in the Himalayas and North-east Hill States of India. P. xanthoschistos has four subspecies breeding in India whereas P. reguloides has two to three subspecies based on different classifications. The objectives of my study were: 1. 2. To study altitudinal and geographical variations in songs of Phylloscopus xanthoschistos and Phylloscopus reguloides along the Himalayas. To examine the role of interspecific aggression in habitat selection among four closely related Phylloscopus warblers along altitudinal gradients using song playbacks. The study carried out fieldwork at 15 sites across Himalayas (including two localities in the Northeast state of Meghalaya) covering all subspecies of the two species. The fieldwork included recording of songs of P. xanthoschistos and P. reguloides and to carry out playback experiments, both intraspecific and interspecific. Intraspecific experiments were carried out to know the significance of geographical song variation, and the interspecific experiments for finding out interspecific aggression among closely related Phylloscopus species. As far as possible different recordings were used for experiment and control playbacks to avoid pseudoreplication..