Biogeography and Endemism of the Birds of Sri Lanka

Abstract

The avifauna of Sri Lanka, although comprising a fewer endemic species as well as a lower percentage of endemism compared to the island’s herpetofauna or ichthyofauna, is still recognized as a unique assemblage of species that paved the way for delimitation of the Ceylonese subregion (peninsular India south of the Godavari basin and Sri Lanka) of the Oriental region in Wallace’s (1876) global map of zoogeography, as it followed the global avifaunal regions proposed by Sclater (1858). Contemporaneous avifaunal delimitations such as the Singhalese subregion of Blyth (1871; the hill range along the western coast of India south of Tapi basin and southern Sri Lanka) as well as the Malabar province of Blanford (1876, 1901; Western Ghats and southern Sri Lanka) have later facilitated the recognition of Western Ghats and Sri Lanka biodiversity hotpsot (Mittermeier et al. 2004; Myers et al. 2000) as a true biogeographical entity delimited mainly based on plant endemism. Although both Blyth and Blanford identified northern Sri Lanka to harbor an Indian avifaunal element, recent molecular phylogenetic evidence suggests Sri Lanka as a local avian endemism center within the hotspot (Wickramasinghe et al. 2017; Jha et al. 2021), especially with some 70 or so subspecific taxa being near-endemic to the island. It is also notable that at least 22 among the 34 bird species endemic to Sri Lanka are found in further restricted ranges, mostly in the perhumid south-western wet zone and the south-central highlands characterized by a uniquely high habitat heterogeneity. Furthermore, members of the families Timaliidae, Pellorneidae and Leiothrichidae representing seven species of the ‘Asian babblers’ in Sri Lanka show remarkably high endemism with four species being endemic to the island, while the other three are also endemic at subspecies level. Such high degrees of endemism have inevitably made Sri Lanka to be recognized as an Endemic Bird Area by the BirdLife International (Stattersfield et al. 1998), also being strongly supported by similar studies for other taxa, especially herpetofauna with insular endemic radiations (Schulte et al. 2002; Bossuyt et al. 2004). Further, identifying the Global 200 priority ecoregions for the conservation of a representative sample of the global biodiversity Olson and Dinerstein (1998, 2002) recognized Sri Lankan moist forests as a spatial conservation priority representing the Tropical and Subtropical Moist Broadleaf Forests Biome of the Indomalayan Realm (Olson et al. 2001). These conservation biogeographical analyses repeatedly highlight Sri Lanka as a landmass with a high bird conservation value that has preserved a considerably important evolutionary history.