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. The outer greater coverts of the Oriental Plover are tipped white (Hayman et a!. 1986) and may appear as a very narrow wing-bar, but it is unlikely to be as clear as that of the bird at Lake Finniss, and the authors have not seen an Oriental Plover showing what they would consider a clear wing-bar. The bird looked too squat to be an Oriental Plover. Three structural features observed by the authors contribute to this: 1. The Oriental Plover has noticeably long tibiae and a tall, erect stance; Caspian Plovers have shorter tibiae and a more horizontal stance. The bird at Lake Finniss had tibiae too short to indicate an Oriental Plover. In direct comparison with a nearby Pacific Golden Plover, the bird at Lake Finniss had distinctly shorter legs. Measurements in Prater et a!. (1986) indicate that the legs of an Oriental Plover should be longer than those of a Pacific Golden Plover, whereas those of a Caspian Plover are shorter, or at the lower end of the range of the length of legs of Pacific Golden Plovers. The missing foot made one leg shorter. Waders are regularly seen standing on one leg when resting, and in many cases have the tibia tucked up, making the legs look short in casual observation. The bird at Lake Finniss was clearly not in such a posture, and the authors have no doubt that the full length of the leg was seen. 2. The primaries of the bird at Lake Finniss projected only slightly beyond the tail, clearly less so than on an Oriental Plover. This short projection of the primaries beyond the tail gave the bird less of an elongated (sometimes described as an 'elegant') appearance than would be expected of an Oriental Plover. Oriental Plovers appear long-winged, with a marked projection of the primaries beyond the tail. The authors have sufficient experience of Oriental Plovers to enable this judgement without a bird present for direct comparison. 3. The bird at Lake Finniss had a shorter neck than would be expected on an Oriental Plover. This was noticeable during the observation while the bird was standing still, feeding, taking flight or alighting, and is therefore not simply a case of its having remained hunched. In the authors' experience, Oriental Plovers appear to have longer necks at all times in similar stances. The legs were dark grey with a dark-green tinge. The legs were scrutinised carefully and the authors saw no evidence that they were muddied or otherwise discoloured. Leg colour of Caspian Plover is described as variable, from pinkish yellow to greyish green to slate-grey, whereas those of the Oriental Plover are 'yellow to orange, tinged fleshy or greenish' (Hayman et a!. 1986). Cox (1988) VOL.18 (2) JUNE 1999 Caspain Plover, Lake Finniss, N.T. 85

reported a variation in Oriental Plover leg colour in a flock of27 birds from 'pinkish­ yellow to yellowish-orange' and, in observing many hundreds of Oriental Plovers, we have not seen one with dark legs. The dark legs clearly indicate that the bird was a Caspian Plover. However, it is conceivable that an individual Oriental Plover could have dark legs. On its own, this feature would be inconclusive, but in context with the other features noted of the bird at Lake Finniss, it strongly supports the identification as a Caspian Plover. The authors were not able to age the bird with certainty, though the densely patterned crown and the distinct pattern of bright edges and dark centres of the back-feathers suggested that it was a juvenile bird. Indeed, the plumage most closely matched an illustration of a juvenile Caspian Plover in Hayman et al. (1986 - illustration 109d). The juvenile upperparts of the Caspian Plover are described as 'distinctly scaled' (Cramp & Simmons 1983), and illustrations and descriptions in Hayman et al. (1986) also suggest that juvenile Caspian Plovers have brighter fringes to the dark-centred back feathers than Oriental Plovers. The Lake Finniss bird matches these descriptions. Plumage descriptions of non-breeding birds (Prater et al. 1977, Cramp & Simmons 1983, Hayman et al.1986) indicate nothing that unequivocally separates Caspian Plover and Oriental Plover, and many plumage features can be found on both species. It would be unwise to identify a vagrant bird, particularly one such as this, on any single characteristic. The combination of features shown by the bird at Lake Finniss conclusively identifies it as a Caspian Plover, and the Birds Australia Rarities Committee has accepted it as such (Case 218).

Explanation of occurrence The Caspian Plover is a long-distance migrant, reaching high latitudes, well south of the tropics, in Africa in the non-breeding season (Hayman et al. 1986). Many long-distance migrants exhibit vagrancy in regions far removed from their usual range. Thus, the occurrence of a Caspian Plover in Australia should not be especially surprising, and perhaps no more remarkable than the occurrence of some other species, such as the Spotted Redshank Tringa erythropus, which rarely cross the Equator in Asia.

Status of records Current published opinion implies that the Caspian Plover at Lake Finniss in October 1994 may be the first or second confirmed record of this species in mainland Australia, depending on the validity of the specimen from Pine Creek. The other claims of the species also were from the Northern Territory.lt is possible that further close scrutiny oflarge Charadrius and Pluvialis plovers in the Northern Territory and north-western Australia may reveal additional sightings.

Acknowledgements Thanks are due to Mr G. Fagan, Manager of Marrakai and Woolner Stations, for allowing us to visit Lake Finniss. Visits to the lake were part of an investigation into movements and populations of the Little Curlew and other waterbirds, conducted by RJ for the Conservation Commission of the Northern Territory.

References Condon, H.T. (1961), 'The Caspian Plover- a new record for Australia', Emu 61, 191-195. AUS1RALIAN 86 McCRIE & JAENSCH BIRD WATCHER

Cox, J.B. (1988), 'Some records and notes on the identification of the Oriental Plover', S. Aust. Ornithologist 30, 120-121. Cramp, S. & Simmons, K.E.L. (Eds) (1983), The Birds of the Western Palearctic, vol. 3, Oxford University Press, Oxford. Gibson-Hill, C.A. (1949) 'The birds of the Cocos-Keeling Islands (Indian Ocean)', Ibis 91, 221- 243. Hayman, P., Marchant, J. & Prater, A.J. (1986), Shorebirds. An Identification Guide to the Waders of the World, Croom Helm, Kent, U.K. King, B., Woodcock, M. & Dickinson, E.C. (1976), A Field Guide to the Birds of South East Asia, Collins, London. Marchant, S. & Higgins, P.J. (Eds) (1993), Handbook of Australian, New Zealand & Antarctic Birds, vol. 2, Oxford University Press, Melbourne. McCrie, N. ( 1984 ), 'Further records of the Oriental Plover and a reassessment of some problems in field Identification', S. Aust. Ornithologist 29, 106-107. McKean, J.L., Thompson, H. A. F. & Estbergs, J.A. (1976), 'Records of uncommon migrant waders near Darwin',Aust. Bird Watcher6, 143-148. Minton, C. (1999), 'NW '98 expedition success', Tattler 18, 3. Prater, A.J., Marchant, J.H. & Vuorinen, J. (1977), Guide to the Identification and Ageing of Holarctic Waders, BTO Guide 17, British 'trust for Ornithology, Tring, U.K. White, C.M.N. & Bruce, M.D. (1986), The Birds of Wallacea, BOU Checklist 7. Received 18 January 1999 •

Erratum Well, the ol' Word Botcher really botched it last issue (18[1 ], March 1999). After everything looked right in a final check of the page-proofs, a duplicate of page 39 was inadvertently printed in place of page 34. This error affected every copy of that issue. The correct page 34 is reprinted and supplied with the current issue, with an extra margin for binding in its correct place at the close of the volume. We apologise to the author, Tony Rose, whose paper was affected. -Editors