Song divergence of Philippine bulbuls (Pycnonotidae) on islands

Bulbuls (Pycnonotidae) are a biologically diverse group of songbirds that produce a variety of vocalisations. Their songs are very audible, yet the vocal behaviour of the majority of bulbul species has not been formally described or subject to bioacoustical study. The Philippine bulbul (Ixos philippinus) is a sedentary and endemic species of the Philippine archipelago. This thesis presents the first detailed descriptions of its song. The songs were recorded on five islands locations that covered eight different habitats. Nine song features of these species were compared, in order to understand song variations between different islands. In searching for correlations, habitat types and geographical distances between the islands were also measured. The songs of the species found on five islands were readily split up into three groups based on end frequency, syllable number and song duration. The correlations possibly relate to a late Pleistocene connection between the islands and colonization routes of the species. It was found that song frequency parameters in bulbul species is primarily affected by habitat, whilst the effect of current distances between islands was shown to be weak