The richness of Sri Lanka’s biodiversity is well reflected by its avifauna. No less than 439 species have been recorded with 236 being resident, 203 migrant and the rest being occasional visitors or vagrants.
This total may well rise to over 450 as a number of new species reliably recorded awaits ratification by the Ceylon Bird Club rarities & records committee (CBCRRC).
Being a tropical island situated at the southern most tip of the South Asia region (now recognized as a significant avifaunal entity) many species occurring in Sri Lanka, other than the endemics, are identical to, or show only minor differences to those occurring in the adjacent Indian mainland.
The high degree of endemism of the island’s avifauna is well demonstrated by the presence of 33 (Rasmussen & Anderton 2005) endemic species and 68 endemic subspecies amongst the resident forms. The majority of the endemic species are found in the wet zone forests or the hills. It is speculated that most of these have evolved to be distinct from those in neighboring India due to long separation from this sub continent of which Sri Lanka is thought to have been a part of earlier. Also some species are thought to constitute a relic fauna whose parent stocks have died off in the mainland.
The number of species considered to be endemic to the island has been fluctuating over the last hundred years or more. Legge considered 47 species to be endemic which was reduced to 21 during the first half of the 20th century (due to the biological concept being widely accepted). Subsequently the number rose to 23 (Sibley and Monroe) and then to 26 (Wijesinghe) until the latest figure has risen to 33 after Rasmussen in her Birds of South Asia ( 2005) elevated a number of species to endemic status in addition to the newly discovered Serendib Scops Owl by fellow member Deepal Warakagoda.
As Sri Lanka is located at the tip of peninsular India, many bird species migrating annually from the northern autumn-winter along the Central Asian-Indian flyway end their southward journey in the island. Similarly, certain pelagic species which migrate from the southern autumn-winter to the Indian Ocean occur within the oceanic limits of the country.
