VOL.18 (2) JUNE 1999 81 AUSTRAUAN BIRD WATCHER 1999, 18, 81-86 Sighting of a Caspian Plover Charadrius asiaticus at Lake Finniss, Northern Territory by NIVEN McCRIE1 and ROGER JAENSCH2 1P.O. Box 41382, Casuarina, N.T. 0811 2Wetlands International- Oceania, G.P.O. Box 636, Canberra, A.C.T. 2601 Summary There have been several reports of Caspian Plov~rs Charadrius asiaticus from mainland Australia, but doubt has been cast over their validity. This paper reports on a sighting of the species at Lake Finniss, Northern Territory. The record has been accepted by the Birds Australia Rarities Committee (Case 218), and may constitute the first confirmed record for the Australian mainland. Separation from similar species is discussed. Introduction The Caspian Plover Charadrius asiatic us breeds on steppes and in semi-deserts scattered through central Eurasia, and winters in eastern and southern Africa (Marchant & Higgins 1993). It is rather similar in appearance to the Oriental Plover C. veredus which breeds farther east, in Mongolia, Manchuria and adjacent regions, and winters in South-East Asia and Australasia (Marchant & Higgins 1993). Normally, therefore, these species do not occur in the same areas. Several occurrences of Caspian Plovers have been documented from southern Asia, including north-western parts of India, Sri Lanka and the Maldives (Hayman & Marchant 1986), and Australia and its territories (Marchant & Higgins 1993), but, to our knowledge, there has been none from South-East Asia (King et al. 1976, White & Bruce 1986). A single specimen was collected from the Cocos­ Keeling Islands on 17 October 1941 (Gibson-Hill1949); a single specimen was collected at Pine Creek, N.T., on 26 September 1896 (Condon 1961); and there are two published reports from near Darwin in 1974 (McKean et al. 1976). Some doubt has been cast on the validity of the specimen from Pine Creek, and the two reports from Darwin are unconfirmed (Marchant & Higgins 1993). In contrast, the Oriental Plover occurs annually in Australia, with records from most states, and sometimes in substantial numbers; for example, 57 000 were counted on Eighty Mile Beach, near Broome, WA., in October 1988 (Minton 1999). The sighting On 5 October 1994, NM and RJ were counting Little Curlews Numenius minutus and other waterbirds at Lake Finniss, N.T. (12°48'S, 131°22'E). Lake Finniss is a near-permanent swamp at the north-eastern edge of the Adelaide River floodplain, about 7 km south of Van Diemen Gulf, and 75 km east-north­ east of Darwin. During the wet season (October-April), it receives inflow mainly from minor creeks, and the water is prevented from draining to the floodplain by natural levees and flow-control structures on two outflow channels. Most of the lake is covered by dense perennial beds of aquatic grass, mainly Hymenachne, and areas of sedge Eleocharis, though there are also areas of open water. Lake Finniss dries up during the dry season, and between September and November the water AUSTRALIAN 82 McCRIE & JAENSCH BIRD WATCHER retreats across the shallow inner basin. Feeding by cattle, feral pigs and many thousands of Magpie GeeseAnseranas semipalmata ensures that the dry margins and surrounds of the lake remain bare or short-grassed at this time. The first series of heavy showers of the wet season may cause quick growth of annual grasses around the shores, and a gradual refilling of the lake and dispersal to the nearby floodplains by waterbirds that had congregated there during the dry season. From 1230 to 1430 h, NM and RJ observed an unusual Charadrius plover on the northern shore of the lake. When first sighted, it was partly hidden in short aquatic grass at the edge of the water. It later moved to exposed situations on bare, dry mud or in shallow pools on the drying lake-bed, and was put to (short) flight several times by the observers. It was viewed with lOx and 12x binoculars and a 25x tripod-mounted spotting scope under strong, nearly overhead light. Other waders nearby, some within a few metres, included Pacific Golden Plover Pluvialis fulva, Australian Pratincole Stiltia isabella and Sharp-tailed Sandpiper Calidris acuminata. The following description of the unusual plover is based on notes and sketches taken by both observers during the observation. Jizz The bird's stance was more horizontal than upright, recalling a Calidris sandpiper rather than an Oriental Plover or (less so) Pacific Golden Plover. The legs and neck were both relatively short. Size The body was slightly smaller than an Australian Pratincole, and significantly smaller than a Pacific Golden Plover, both of which were close by, enabling a clear comparison. In size, the bird was more similar to a Sharp-tailed Sandpiper than to a Pacific Golden Plover. The legs were noticeably shorter than those of a Pacific Golden Plover. Bare parts The legs were dark grey, with a dark-green tinge, and, especially the tibiae, appeared short for one of the larger plovers (too short for Oriental Plover), and were certainly shorter (particularly the tibiae) than the legs of a Pacific Golden Plover. In flight, the toes extended slightly beyond the tail. The bird's right foot was missing. The bill was slender and relatively long for a plover, the length being approximately equal to the length of the head, or slightly less. The bill was grey, darker at the tip, and, in profile, was not 'chisel-shaped' like the bill of a Pacific Golden Plover. The eye was large and typically plover-like; the iris was dark, and there was a distinct but narrow white orbital-ring. Head The crown was buff with dark streaks. The supercilium was buff-white, curving over the eye and extending well back to the side of the nape. The face was greyish VOL.18 (2) JUNE 1999 Caspain Plover, Lake Finniss, N.T. 83 brown and buff, and the lores were not dark. There was a small area of white on the frons. The auriculars were dark, with a dark area separate from the eye and the nape. The hindneck was streaked brown, darker in the centre. Upperparts The centre of the back and scapulars were strongly marked with dark feathers (black or dark brown) with rufous fringes. The upperwing coverts were grey-brown, with broad pale edges. The greater coverts were very pale, giving the appearance of a pale patch on the standing bird. In flight, the upperwing showed a narrow white wing-bar from the body to the centre of the wing. On the standing bird, the wings extended past the tail slightly. The rump was plain grey-brown and the tail dark, narrowly fringed white. Underparts The throat and chin were white. The breast was mottled dark grey-brown, streaked above and abruptly demarcated from the belly, which was off-white or slightly grey. The underwing was off-white to white, paler in the basal half, contrasting not with the belly but with the darker chest. The undertail coverts were white. The unusual plover was not seen on a later visit, on 22 October 1994, at which time the shoreline had altered since further drying of the lake. By November, refilling of the lake and revegetation of the surrounds had begun, and thus the habitat was probably then unsuitable for Charadrius plovers. Discussion Diagnosis Neither NM nor RJ is familiar with Caspian Plovers in the field, though NM has studied skins of this species in the South Australian Museum (McCrie 1984). Both authors are very familiar with Oriental Plovers, both in breeding and non­ breeding plumage. Close observations of an Oriental Plover near Darwin from mid to late October 1994 reinforced the authors' conclusions. For distinction between these species we relied chiefly on the descriptions of the Caspian Plover in Hayman et al. (1986) and Cramp & Simmons (1983), and on the field and museum studies reported in McCrie (1984) and Cox (1988). The bird was clearly neither a Greater Sand Plover C. /eschenaultii nor a Lesser Sand Plover C. mongo/us. We consider that the unusual plover at Lake Finniss was not a Pacific (or other) Golden Plover for the following reasons: 1. The bill was too slender and straight, not robust and chisel-shaped as in the Pacific Golden Plover. 2. The body was smaller and the legs shorter than on a nearby Pacific Golden Plover. 3. The underwing was lined with white, and did not contrast with the belly (whereas in non-breeding plumage of the Pacific Golden Plover the underwing is grey and contrasts with the paler belly). 4. The upperparts lacked conspicuous pale or golden spots (present in all plumages of all Pluvialis species). AUSTRALIAN 84 McCRIE & JAENSCH BIRD WATCHER Separation from the similar Oriental Plover is more difficult. The bird at Lake Finniss clearly showed a whitish underwing when it was seen in flight, or when it lifted its wings when standing on the ground. The underwing coverts were concolorous with the abdomen, and contrasted strongly with the breast. Whitish underwing coverts are a characteristic of the Caspian Plover and safely rule out an Oriental Plover, which has brown or dark-grey underwing coverts. In comparing specimens at the South Australian Museum, Cox (1988) noted that the underwing of the Oriental Plover 'exhibits a rather uniform coloration of dark grey-brown', whereas on the Caspian Plover, the underwing appears 'mainly whitish with darker primaries'. In flight, the upperwing showed a narrow but distinct white wing-bar from the body to the centre of the wing. Views of the upperwing were rather poor, and detailed assessment of the extent of the wing-bar was difficult. The presence of a clear white wing-bar is characteristic of the Caspian Plover.