Pelagic seabirding off Cape Town, RSA : 1

by Callan Cohen, Claire Spottiswoode and Barrie Rose, from Bulletin of the African Bird Club, volume 8.1, March 2001.

Approaching a fishing trawler off the continental shelf near Cape Town is a birding experience that remains engraved in the memory forever. The opportunity to see thousands of albatrosses of up to seven species just an arm's length away is luring increasing numbers of birders to Africa's southern tip. Day trippers in winter regularly see over 10,000 seabirds of up to 30 species, making it arguably the world's most mind-blowing yet accessible seabirding experience. Furthermore, if you are a hardened seawatcher (or a weakened seafarer!), the Cape Peninsula also offers some of the world's best land-based seabirding. In addition to the petrels and albatrosses that flash beyond the waves in blustery conditions, the coastal areas hold endemic specialities such as Bank Phalacrocorax neglectus and Crowned Cormorants P. coronatus, migrant Antarctic Terns Sterna vittata in winter, and even a chance of Greater Sheathbill Chionis alba.

Crowned Connorant, South Africa (Callan Cohen)

The Cape's amazing seabird abundance and diversity are products of the Benguela current that originates in the icy waters of Antarctica. Surging up the west coast of southern Africa, the nutrient-rich waters cause upwellings along the continental shelf, nurturing a profusion of ocean life that supports both a lively fishing industry and vast numbers of seabirds. Pelagic species congregate around the trawlers, making them easy to locate and approach. The high point of a pelagic birding trip is trailing behind a trawler with up to 5,000 birds squabbling for scraps in its wake. The diversity of seabirds is highly seasonal, so consult the monthly table (below), compiled from over 300 pelagic birding trip lists during the past ten years. This will help you to decide when best to go in order to maximise the chances of seeing your most- wanted species. Note that seabird numbers fluctuate from year to year, and that birding in the vicinity of a trawler will make a huge difference to your trip.

Winter trips
Winter (May-September) is the most spectacular time at sea. Huge numbers of albatrosses and other pelagic seabirds migrate northwards from their breeding sites as far south as Antarctica, moving into Cape waters to escape the harsh polar winter. Shy Diomedea cauta and Black-browed Albatrosses D. melanophrys are abundant, and both subspecies of Yellow-nosed Albatross D. chlororhynchos are commonly seen in small numbers.
Recent research on albatross taxonomy, based on molecular analysis and embracing the Phylogenetic Species Concept, has suggested that there are ten unrecognised species of albatross in the world. These tentative 'new' species are currently classified as sub-species, but should they be recognised as full species, the global albatross species total would rise from 14 to 24. In this article and the seabird seasonality table, the proposed 'new' species that can be distinguished at sea are treated separately to draw attention to these taxa. In particular, pelagics off Cape Town are the most accessible place globally to see the Atlantic 'grey-headed' chlororhynchos subspecies of the Yellow-nosed Albatross (see photo). There is also always a chance of seeing the rare Royal D. epomophora and Grey-headed Albatrosses D. chrysostoma.

Yellow-nosed Albatross (Bruce Dyer)

The prize of a winter trip must however be the Wandering Albatross D. exulans, which has become scarcer in recent years. Research is demonstrating that the comparatively recent advent of longline fishing techniques is causing a tragic number of deaths among Southern Hemisphere seabirds. Fishing lines as long as 100 km, studded with up to 20,000 baited hooks, are trailed behind fishing vessels. It is estimated that a staggering 100 million hooks each year are set in the southern ocean alone. As the line is lowered into the water, but before it sinks very deep, seabirds following the boat plunge down to grab the bait, become ensnared and drown. Research estimates suggest that as many as 40,000 albatrosses are killed annually, a disturbing figure which is causing population declines in several species. These declines are potentially devastating, especially among the long-lived Wandering Albatross, a species which only raises one chick every two years. Wandering Albatross is now rare on the fishing grounds, where up to 40 could be seen attending a single trawler in the 1950s. Currently, the Global Seabird Programme of BirdLife International and other concerned parties are investigating ways of reducing this seabird mortality. Visit www.uct.ac.za/depts/stats/adu/seabirds for further details.

On a more positive note, a number of winter trips last year encountered all of the above seven albatross taxa on a single day: Wandering, Royal, Shy, Black- browed, Grey-headed and both subspecies of Yellow-nosed!

The ever-present White-chinned Petrels Procellaria (a.) aequinoctialis, Sooty Shearwaters Puffinus griseus and Cape Gannets Sula capensis are joined by huge numbers of flashy Pintado Petrels Daption capense, Broad-billed Prions Pacbyptila vittata (subspecies desolata is the most common) and Wilson's Storm-Petrels Oceanites oceanicus. Both Northern Macronectes balli and Southern Giant Petrels M. giganteus are invariably present in small numbers, usually one or two per trawler, and even the Southern Fulmar Fulmarus glacialoides makes an occasional appearance. The rare Spectacled Petrel Procellaria (aequinoctialis) conspicillata could be encountered at any time of year. The 'Ringeye', as it is more affectionately known, was only recently split from White-chinned Petrel. (This taxonomic decision, based largely on the breeding calls, bestows upon it the dubious distinction of being one of the world's most threatened seabirds, breeding only on Inaccessible Island in the South Atlantic Ocean. Alarmingly, it is believed that as much as 5% of the population is killed annually by longline fishing off Brazil.) Watch out for the occasional fast-flying Soft-plumaged Petrel Pterodroma mollis whipping by, especially away from the trawlers. Small flocks of terns, including Antarctic Tern, fly by in coastal areas, and Subantarctic Skuas Catharacta antarctica are invariably in attendance at every boat, and are often seen even before leaving False Bay.

Summer trips
From October to April, North Atlantic seabirds migrate south to claim their share of the Benguela's bounty. Although seabird numbers are generally lower during this period than in winter, summer trips are spectacular nonetheless and provide an opportunity to see several additional species.
The three most common albatrosses, the two giant petrels (uncommon), White-chinned Petrel and Sooty Shearwater are always present. They are joined in summer by Cory's Shearwater Calonectris diomedea (mainly the nominate subspecies diomedea, sometimes known as Scopoli's Shearwater) and Great Shearwater P. gravis, along with smaller numbers of Soft-plumaged Petrels (early summer), the occasional Spectacled Petrel and Manx P. puffinus and Flesh-footed Shearwaters P. carneipes. The majority of Great-winged Petrels Pterodroma macroptera make their appearance only at this time, having spent the harsh Antarctic winter at their breeding grounds further south. Significant numbers of European Storm-Petrels Hydrobates pelagicus join the ever-present Wilson's Storm-Petrels. White-bellied Storm-Petrel Fregetta grallaria is present only in small numbers, as a passage migrant, in late September/October and again in April.

In Cape waters, Leach's Storm-Petrel Oceanodroma leucorhoa is mainly seen only far offshore beyond the continental shelf, and it was hence assumed to be an exclusively non-breeding migrant from the Northern Hemisphere during our summer months. However, this species was discovered as recently as 1997, by Phil Whittington, to be breeding on Dyer Island off the Cape's south coast, making it the only pelagic seabird breeding in sub-Saharan Africa. Up to 20 pairs breed on the island annually, and can be heard calling at night from their nesting burrows deep in the old stone walls that surround the island's few buildings.
The common Arctic Stercorarius parasiticus, uncommon Pomarine S. pomarinus, Subantarctic and very scarce Long-tailed Skuas S. longicaudus patrol the skies closer inshore. Arctic Tern Sterna paradisaea is a passage migrant, although it is seen in smaller numbers throughout the summer, along with Sabine's Gull Larus sabini. lucky observers may see small flocks of Grey Phalarope Phalaropus fulicarius.