June 2010 209 Antarctic Terns, Sterna vittata, on Kangaroo Island, South Australia with an analysis of their possible race and origin. CHRIS BAXTER Abstract separated from the smoky-grey chin and throat by a distinctive white facial streak (Figure 1). During September 2006, the first positive sighting of Tail and rump are white without obvious black Antarctic Terns, Sterna vittata, in Australia occurred edging to the outer rectrices. Underbody smoky- at Cape du Couedic on the SW corner of Kangaroo grey with translucent white remiges and narrow Island (KI), South Australia. Previously, the only tapering dark trailing-edge to primaries. The, confirmed occurrences of this species in Australia legs and feet are bright red and the tail becomes were two specimens collected from SA and WA. more deeply forked during breeding due to growth of long outer tail feathers (rectrices - Initial discovery on 1 September 2006 was of three streamers) (Harrison 1983; Higgins and Davies birds roosting amongst numerous Crested Terns, 1996; Environment Australia 2005). Thalasseus bergii, and White-fronted Terns, Sterna striata. From this time until the date of last sighting Non-breeding (basic) plumage features pale- on 26 September 2006, ornithologists came from all grey upperparts, white fore-crown, frons, lores, over Australia to observe these birds. During this rump and tail. Underparts white - sometimes period a total of 10 birds were positively identified smudged with patches of smoky-grey. Hind- and many photographs taken. The record was crown, nape and sides of face are black with approved by Birds Australia Rarities Committee dark red bill, legs and feet (Harrison 1983; (BARC Case 525) on 25 March 2007. Higgins and Davies 1996). (Figure 2). This paper documents the first confirmed record of Current taxonomic classification of this species live Antarctic Terns in Australia and discusses the generally acknowledges five races (Higgins and observations in some detail. Much of the discussion Davies, 1996). They are listed here with their deals with the finer diagnostic features of these birds respective breeding islands. and searches for clues as to the race and origin of S. v. vittata Gmelin, 1789 – Southern Indian these extremely rare visitors. Ocean (Heard Is, Kerguelen Is, Prince Edward Is, Marion Is, Crozet Is). INTRODUCTION S. v. tristanensis Murphy, 1938 – South Atlantic/ Southern Indian Ocean (Tristan da Cunha Is, Gough Is / Amsterdam Is, St. Paul Is) The Antarctic Tern is a medium-sized sea tern (length 32-36 cm; wingspan 72-79 cm; weight S. v. gaini Murphy, 1938 – South Atlantic (S Shetland 140-160 g) similar in appearance to the Arctic Is, Antarctic Peninsula and associated islets). Tern, Sterna paradisaea, and the Kerguelen Tern, S. v. georgiae Reichenow, 1904 – South Atlantic S. virgata, but is bigger and bulkier, with heavier (South Georgia Is, South Orkney Is, South bill, legs and feet (Higgins and Davies 1996). Sandwich Is and Bouvet Is). Breeding (alternate) plumage is distinctive S. v. bethunei Buller, 1896 – Southern Ocean/ with pale-grey upperparts, extensive and South Pacific (Macquarie Is, Stewart Is, Snares pronounced black cap extending from the nape, Is, Auckland Is, Bounty Is, Antipodes Is and crown and face to the forehead. The black cap is Campbell Is). 210 South Australian Ornithologist 35 (8) Figure 1. Breeding plumage Antarctic Terns at Atlas Cove, Heard Island on 26 April 2005. Neil Cheshire. Tree and Klages (2004) listed the temperate (1500 pairs); race georgiae on South Georgia Indian Ocean population on St Paul and Is (2 500 pairs), South Orkney Is (500 pairs), Amsterdam Is as S. v. santipaula. Also, some South Sandwich Is (100 pairs), Bouvet Island (50 taxonomists split NZ race S. v. bethunei into pairs) and race tristanensis on Tristan da Cunah two races – the population at Macquarie Is and Gough Is (1 159 pairs). In the S. Indian being classified as S. v. macquariensis. This Ocean race vittata breeds on Kerguelen Is (2 000 paper does not follow either of these taxonomic pairs), Heard Is (Aust. 100 pairs), Crozet Is (100 classifications – preferring to follow Christidis pairs) and Prince Edward Is (<15 pairs). Race and Boles (2008) and Higgins and Davies (1996) tristanensis breeds on Amsterdam and St Paul Is and lumping those populations within races (400 pairs). The Indian Ocean population is just tristanensis and bethunei respectively. over 2 630 pairs. The Antarctic Tern is chiefly a circumpolar In the S Pacific/Southern Ocean race bethunei inhabitant of Antarctic and subantarctic breeds on southern New Zealand Is (Stewart, regions to 68 S (Higgins and Davies 1996). It is Snares, Auckland, Bounty, Antipodes and widespread and breeds on remote subantarctic Campbell Is – 1000 pairs) and Macquarie Is islands and the Antarctic Peninsula throughout (Aust. c 40 pairs). Pacific Ocean total 1040 pairs. the S Atlantic, S Indian Ocean and islands to World total population an estimated 44, 455 pairs the S of New Zealand (Rootes 1988; Harrison (Tree and Klages 2004). 1983; Rounsevell and Brothers 1984; Robertson and Bell 1984; Williams 1984; Weimerskirch et Part of the population moves N during the al. 1989; Higgins and Davies 1996; Garnett and austral winter, moulting into basic plumage and Crowley 2000). spending the non-breeding season (April-May to Sept -Oct) on the SE coast of S America (Tierra An estimated 40 800 pairs (c 92% of the total del Fuego N to Rio de Janeiro) and on the W breeding population) breed in the S Atlantic, and E coasts and off-shore islands of S Africa to chiefly race gaini breeding on the South Shetland as far N as c 30 S (Blake 1977; Brooke et al. 1988; Is (35 000 pairs) and the Antarctic Peninsula Higgins and Davies 1996; Tree and Klages 2004). June 2010 211 Brooke et al. (1988) estimated the South Africa region during the period November-March. wintering population to be in excess of 15 000 Non-breeding immature birds may be present birds. Tree and Klages (2004) estimated it to be throughout the year. It helps that Antarctic 12 800 during August 2001, with roosts of up to Terns should be in breeding plumage when 4 000 on both Dyer and Dassen Is and in excess these two Northern Hemisphere visitors are of 5 000 on Bird Is. in non-breeding plumage. However, during arrival (November) and departure (March), The Antarctic Tern is a vagrant to Australia. Arctic and Common Terns may have retained/ Prior to the record reported in this paper there acquired some degree of breeding plumage and were only two records, both specimens. An are then much more difficult to distinguish from adult in non-breeding plumage, collected at Antarctic Tern. The movements of the Antarctic Metricup, WA, 35 km SSW of Busselton, 21 July Tern are not fully understood due to confusion 1978 (WAMA15670) (Higgins and Davies 1996) with other terns, especially at the sub-species and an individual, probably adult, moulting into level (Harrison, 1983; Higgins and Davies 1996; summer dress, collected on S Casuarina Islet, Garnett and Crowley 2000). The non-breeding off SW Kangaroo Island (KI), SA, 23 November range of most populations is poorly known 1982 (SAM B36933) (Copley 1996; Higgins (Higgins and Davies 1996). and Davies 1996; Baxter and Horton 2008). Finally, a single Antarctic Tern was observed THE RECORD and photographed by ten pelagic birders part way between the edge of the continental shelf On Friday, 1 September 2006, three Antarctic and Pedra Branca, S of Tasmania on 29 July Terns, Sterna vittata, were observed at Cape du 2008 (Wakefield 2008) and this record was also Couedic in Flinders Chase National Park, on the accepted by BARC (Case 582). There are no SW corner of KI, South Australia (pers. obs.). confirmed records off the NZ mainland (Higgins They were roosting with c. 1 000 Crested Terns and Davies 1996). Thalasseus bergii and 112 White-fronted Terns S. striata on a rocky platform alongside Admirals Breeding takes place mainly between Arch – a very popular tourist attraction of October and March, although this varies with national and international significance. Also geographical location and changing climatic hauled out here were hundreds of New Zealand conditions and food availability (Downes et al. Fur Seal, Arctocephalus forsteri, and a small 1959; Higgins and Davies 1996). Only two races number of Australian Fur Seal, A. pusillus breed in Australian territory. S. v. vittata breeds doriferous. on Heard Is (53 05’ S; 73 33’ E) in the S Indian Ocean (Figure 1). Race S. v. bethunei breeds on One of the Antarctic Terns was in advanced Macquarie Island (54 39’ S; 158 53’ E) in the moult into breeding plumage with almost Southern Ocean, 1 500 km SSE of Tasmania. The fully black cap, smoky-grey underparts and latter island is approximately half way between a distinctive white facial streak. The other Australia and Antarctica. two were in non-breeding plumage, with blackish nape and hind-crown contrasting Antarctic Terns are very similar in appearance with pronounced white fore-crown, frons and to the Arctic Tern, Common Tern, S. hirundo, underparts (pers. obs.). Observation of these Kerguelen Tern and South American Tern, S. birds was from a designated boardwalk and hirundinacea. Great care must be taken with viewing platform constructed by SA National identification in the field, particularly with Park and Wildlife (SA NP&W) to protect the the former two species which are regular integrity of the fur seal colony and surrounds. non-breeding visitors to the Australasian The closest viewing platform was c.50 m distant 212 South Australian Ornithologist 35 (8) Figure 2. Basic plumage Antarctic Tern with primary moult in progress at Cape du Couedic, KI, September 2006. David Harper.