Watching seabirds on the West Coast of Sri Lanka: 1by Rex I. De Silva, from OBC Bulletin 26, November 1997. Although the majority of birders visiting Sri Lanka concentrate on searching for the endemic species, they overlook the fact that the west coast provides an opportunity for observing some truly exciting seabirds From an ornithological point of view Sri Lanka can be considered to be an oceanic island - it is bounded on all sides by the Indian Ocean. (1) Nearly fifty seabird species have been recorded on the west coast of Sri Lanka, (2) of these five are known to breed and three are suspected to do so. (3) The remaining species include several winter visitors, a few passage migrants, a summer breeding visitor and a number of vagrants, stragglers, and species whose status is currently uncertain. While the entire coast of the island is suitable for watching seabirds, most of the northern and eastern areas cannot currently be visited on account of a military conflict, hence, this article confines itself to the subject of seawatching on the western and south-western coast. The best season for seawatching is during the south west monsoon (usually May - October). Several species enter coastal waters at this time, among these are the Wedge-tailed Shearwater, Puffinus pacificus, Wilson's Storm-petrel, Oceanites oceanicus, Lesser Frigatebird, Fregata ariel, Brown Skua, Catharacta antarctica, Pomarine Skua, Stercorarius pomarinus, Brown Noddy, Anous stolidus, Lesser Noddy, Anous tenuirostris. A mass-migration of Bridled Terns, Sterna anaethetus, takes place during the south-west monsoon. This migration, which usually begins around June/July and continues until October/November, is often a spectacular phenomenon.
In favourable years as many as 400,000 birds fly southwards during daytime - well within sight of land. (4) The most intensive movement occurs for a week or two in (either) August or September when, in the early mornings, 2,000 to 3,000 birds may fly south in a single hour, well within view of an observer on the beach. (5) The migrating Bridled Terns are at times accompanied by small numbers of Sooty Terns, Sterna fuscata, skuas, boobies and shearwaters. Both the Pomarine and Brown Skuas kleptoparasitise the migrating terns by stealing their catches whenever opportunities arise. At present the area (or areas) of origin of the migrants is not known, nor is their ultimate destination. It is suspected that the migration is a post-breeding dispersal of birds nesting in possibly the Red and Arabian seas, Makran coast of Pakistan and the Maldives. (As there is no reliable information regarding the migration at night, an observer equipped with a good night-vision scope could contribute useful information). A less spectacular but equally interesting phenomenon which takes place during September and October is the southward migration of Flesh-footed Shearwaters Puffinus carneipes. These birds leave their breeding grounds in South-west Australia each May and embark on a lengthy "continuous migration" which takes them north and west to the Arabian Sea and thence southwards past Sri Lanka, back to their homes in time for the next breeding season. (6) Using telescopes, the birds are best seen from shore as they engage in their characteristic version of low-level dynamic soaring; even so they are only observed with some difficulty as the shearwaters never approach closer than about 1.5 km to land. Detailed observations are therefore best conducted out at sea. Two interesting species which visit during the monsoon are the Roseate Tern, Sterna dougallii (our only summer breeding visitor) which nests on small islets off the south-western coast around June/July, and the Red-billed Tropicbird, Phaethon aethereus, a species which is frequently seen on the stretch of coast between Ambalangoda and Galle. The intermonsoonal period (October/November) brings large numbers of Wilson's Storm-petrels relatively close inshore but, on account of their small size and habit of keeping close to the waves, they are not easily seen from land, hence they are best viewed out at sea. It is possible that these birds use Sri Lankan waters as a final staging area prior to their long return journey to breed in Antarctica. The intermonsoon period also heralds the appearance of winter visitors (although small numbers may arrive earlier). Two of these species, the Pallas's Gull, Larus ichthyaetus, and Heuglin's Gull, Larus heuglini, are mainly confined to the north-western coast, although some individuals do stray further southwards along the western seaboard. The Black-headed, Larus ridibundus, visits in small numbers whereas the Brown-headed Gull, Larus brunnicephalus, is rather common at this time of year. The Herring gull, Larus argentatus, is a scarce visitor to more remote areas of the coast. Many of our terns are winter visitors and species present in some numbers at this time are the Gull-billed Tern, Gelochelidon nilotica (a small population may also be resident), Lesser Crested Tern, Sterna bengalensis, Common Tern, Sterna hirundo, Whiskered Tern, Chlidonias hybridus (very common), and White-winged Tern, Chlidonias leucopterus. The Sandwich Tern, Sterna sandvicensis, appears to be a regular visitor in very small numbers. A species which probably visits more frequently than the records suggest is the Black Tern, Chlidonias niger, which, in its winter-plumage, is easily overlooked among the White-winged Terns with which it sometimes associates. The Caspian Tern Sterna caspia, Little Tern, Sterna albifrons, and Large Crested Tern, Sterna bergii, are breeding residents present throughout the year. Nesting areas of these species include small islets off the coast, the shallow banks known as 'Adam's Bridge' in the north-west, as well as the margins of larger 'tanks' (artificial irrigation reservoirs) and lagoons. The Gull-billed, Whiskered and Common Terns have been suspected of breeding in Sri Lanka, but conclusive evidence of this is lacking (3).
Perhaps the most exciting aspect of seawatching on the west coast is the possibility of identifying rare vagrants and stragglers which turn up from time to time. (2, 6, 7) It should be noted that many of the species listed below are based on sight records and include some species not yet officially accepted onto the Sri Lankan list. Hence further observations will obviously be of great value. Among the interesting vagrants visiting coastal waters are several species of petrels including the Cape Petrel, Daption capense, White-headed Petrel, Pterodroma lessonii, Soft-plumaged Petrel, P. mollis, Barau's Petrel, Pterodroma baraui, and Jouanin's Petrel, Bulweria fallax. Several species of Shearwater also come within the category of 'rare vagrants' including the Streaked Shearwater, Calonectris leucomelas, Short-tailed Shearwater, Puffinus tenuirostris, and Audubon's Shearwater, Puffinus lherminieri. (It is interesting to note that as a sighting of Sooty Shearwaters, Puffinus griseus, has come from the east coast, individuals could possibly turn up on the west coast, hence birdwatchers should be on the alert for this species). Among the other vagrants recorded are the Red-footed Booby, Sula sula, Masked Booby, Sula dactylatra, (probably more common than the records indicate), Christmas Island Frigatebird, Fregata andrewsi, Parasitic Jaeger, Stercorarius parasiticus, South Polar Skua, Catharacta maccormicki, Sooty Gull, Larus hemprichii, and White-cheeked Tern, Sterna repressa. |
