by Charles Anderson

Whale Watching
With Americans Corey and Diane Rusk I spent 14 days whale watching off the south coast this April. We went out with the Mirissa Water Sports boat Spirit of Dondra every day from 9 to 22 April 2008. We were joined by Jetwing naturalist Anoma Alagiyawadu from the Lighthouse Hotel on all but one day and by Gehan de Silva Wijeyeratne (CEO, Jetwing Eco Holidays) on 3 days.

Blue Whales were by far the most commonly encountered species, with sightings on 14 out of 14 days (and an average of 4.5 sightings per day). This makes the south coast of Sri Lanka one of the very best places to see Blue Whales in the entire world. I believe that most of these Blue Whales are on migration, en-route from their NE monsoon feeding grounds off Trincomalee to their SW monsoon feeding grounds in the Arabian Sea. However, most of the Blue Whales seen during our trips were not obviously travelling westward. Rather, they were repeatedly diving in localized areas, presumably feeding. So perhaps they are on passage, but having found food off the south coast are quite happy to loiter as long as the food remains. Clearly there is still a lot to be learnt about these whales.

Sperm Whales were also present, with pods being seen on five occasions. While most Blue Whales were seen over the continental shelf, Sperm Whales tended to occur a bit further offshore, in the shipping lanes. And this gives a clue as to why there are so many whales here. A glance at any chart of the Indian Ocean shows that Dondra Head is the southern-most point not only of Sri Lanka, but also of the entire Indian subcontinent. Any ship wanting to pass between east and west has to pass by Dondra. And so too does any cetacean. Furthermore, off Dondra the continental slope comes to within less than 3 nautical miles of the coast. With the seasonally changing monsoon currents producing seasonally changing blooms of plankton; with the land masses of India and Sri Lanka acting like an inverted funnel to channel cetacean movements; and with deep water so close to shore, it is perhaps not surprising that the southern tip of Sri Lanka is such a cetacean hotspot.

Other cetacean species seen were: Bryde’s Whale, Dwarf Sperm Whale, unidentified Beaked Whale, Spinner Dolphin, Striped Dolphin and Indo-Pacific Bottlenose Dolphin.

Seabird Watching
Among the seabirds, Whiskered and several other Terns were seen relatively close to shore. However, most of the ‘more interesting’ species were seen a few miles off, and would not have been visible to a land-based observer.

Shearwaters were seen in reasonable numbers. All were medium-large, all-brown birds. Most Shearwaters (38) were seen on or after 19 April. Some of these birds were definitely, and most were probably, Flesh-footed Shearwaters. They were nearly all heading west, presumably on their annual migration across the Indian Ocean from SW Australia to the upwelling areas of the Arabian Sea. Wedge-tailed Shearwater and Sooty Shearwater were also recorded.

Pomarine Skuas were relatively common, and also relatively easy to identify since more than half were in breeding plumage with full tail extensions (‘spoons’). All Pomarine Skuas seen were heading eastward, towards the Bay of Bengal. This was in marked contrast to most other birds, which were heading west. The peak passage of Pomarine Skuas occurred during 14-19 April (74 birds), with greatest numbers on 17 April (25 definite and 20 probable birds).

While nearly all the Skuas seen were identified as Pomarine (or probable Pomarine) Skuas, three birds were thought to be Arctic Skuas. Two could not be identified with absolute certainty, but one (seen on 19 April) showed classic tail projection and colouration of an adult pale phase bird, and was positively identified as Arctic.

The commonest seabird seen was the Bridled Tern. Hundreds were seen most days, with many in feeding flocks of 30-400 individuals. Most were heading westwards. There is a relatively well-known southward migration of Bridled Terns along the west coast of Sri Lanka, peaking in August-September. Perhaps these April birds are part of the return migration. The smallest numbers of Bridled Terns (10s rather than 100s) were seen on 14-19 April inclusive. Intriguingly, these were the exact days on which the largest numbers of Pomarine Skuas were recorded. Coincidence? Or might the presence of relatively large numbers of Pomarine Skuas have driven the Bridled Terns further offshore?

Among the ‘white’ terns, the commonest was the White-winged Tern. Most were either moulting into, or already in, their beautiful breeding plumage. This made them easy to identify, which is not always the case for birds in non-breeding plumage. Nearly all the White-winged Terns seen were heading westward, and were presumably on passage towards their central Eurasian breeding grounds. Exceptions were seen late in the day (after about 1500h) when some birds were seen flying eastward, perhaps towards local roosting sites. Most sightings were of single birds or small loose flocks, but 100+ were seen in one extraordinary feeding flock with Bridled Terns on 21 April.

Noddies were recorded on four days, always in association with feeding flocks of Bridled Terns. Those that were seen closely enough were all identified as Black Noddies. However, there is a bit of a problem with the taxonomy of small Noddies in the Indian Ocean, with confusion over the separation and ranges of Black and Lesser Noddies (Anous tenuirostris) still not fully resolved.

Dr. Charles Anderson is a professional marine biologist who has lived and worked in the Maldives since 1983. His research on whales there led him to believe that Blue Whales should be present off the south coast of Sri Lanka in April, a hypothesis which he confirmed with visits in April 2007 and 2008. He can be contacted on: anderson@dhivehinet.net.mv or charles.anderson11@btinternet.com .