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Case Summary for:
Submission No 218: Caspian Plover Charadrius asiaticus, Lake Finniss, NT, 5 October 1994. Submitted by Niven McCrie & Roger Jaensch. Verdict: Accepted This case relates to the sighting of a plover seen by two observers on 5 October 1994 at Lake Finniss; which is a near permanent swamp on the NE edge of the Adelaide River flood plain, 7.0 km South of the shore of Van Dieman Gulf and 70 km ENE of Darwin, NT. (12º 22’S 131º 29’E). The bird was observed in strong light from 1230 to 1430hrs. Direct comparison was made with nearby Pacific Golden Plover Pluvialis fulva, Australian Pratincole Stiltia isabella and Sharp-tailed Sandpiper Calidris acuminata. Both observers are well known local ornithologists who are very familiar with the more regular species of the area and in particular Oriental Plover C. veredus. This familiarity was noted by the committee to be a significant factor in this case. The bird was not seen subsequently despite an attempt 22 October 1994 to relocate it. The submission includes field notes (from both observers) a sketch and a written account detailing the circumstances of the sighting. The bird was described as having a stance more horizontal than upright, closer in this respect to a Calidrid sandpiper rather than Oriental Plover. Size was significantly smaller than nearby Pacific Golden Plover but larger than Sharp-tailed Sandpiper. Bill grey darker at the tip with a very long profile, legs dark-grey and rather short with the tibia noticeably shorter than Pacific Golden Plover. One foot was reported to be missing. Toes extending slightly beyond the tail in flight. A dark eye with a distinct but narrow eye-ring. The throat and chin white. Upper-chest streaked dark grey-brown; mid chest mottled dark grey-brown and strongly demarcated from off-white or slightly grey lower chest and belly. Importantly, the underwing was noted to be off-white to white, whitest in the secondary portion of the underwing. The upperparts included a small area of white on the forehead with a streaked buff crown. Face generally buff to greyish-brown. Lores not dark. Supercillium buff-white, curving over the eye and extending to the sides of the nape. Feathers on centre of back and scapulars described as black or dark brown (dark-grey by one observer) with rufous fringes. Upperwing covers grey-brown, broadly edged pale grey. Greater coverts particularly pale. Tail dark, narrowly edged white. The wings were noted to project slightly beyond the tail. In flight a narrow white wing-bar was present across the centre of the upperwing from the body to about the base of the primaries. After significant research and two rounds of voting the committee generally agreed with the observers conclusions. However, some problems in the description did cause concern between members, particularly as the age of the bird could not be determined. One member was of the dissenting opinion that the following features of the description mitigated against a positive vote: The length of the bill "approximately equal to length of head" and further defined as being the length from the "bill base to nape, or slightly less". He felt that this was twice as long as it should appear in Caspian Plover; The colour of the feathers on the centre of the back and scapulars viewed in strong light described as being "black or dark brown" by one observer and then "black or dark grey" by the other observer. He considered that there was no evidence to show that Caspian Plover could ever be this dark on the back. Also commented upon was the fact that this bird only had one foot, potentially removing any credibility relating to the description of the birds posture. Head Pattern: The description mentions a small area of white on the frons (forehead) and a long buff supercillium. Several members of the committee were concerned that more emphasis was not placed on the forehead and supercillium, which by all accounts should be quite striking in the field. Having said that, this feature has been depicted fairly well in the sketch provided and supports Caspian Plover. Bill length: The estimation of the bill length is clearly too long for this species or any comparable plover. However, general consensus was that the sketch supports the description of a bill that is too slender for a sand-plover or a Pacific Golden Plover and therefore closer to that expected for a Caspian Plover. It is also drawn to more acceptable proportions. Upperparts and upperwing coverts: The upperparts are described as black or dark brown with rufous fringes, but innerwing coverts as grey-brown, broadly edged pale grey, with greater coverts especially pale, giving the effect of a pale patch on a standing bird. If the bird were in full fresh non-breeding plumage, the fringes of the upperparts and inner upperwing-coverts ought to be similar rufous-buff (Hayman et al. 1986), not rufous on mantle and scapulars versus pale-grey on the wing-coverts with a paler panel on the greater coverts. Similarly on a fresh first immature non-breeding bird, the upperparts are rufous-fringed as in adults, but the retained juvenile innerwing-coverts are rather narrowly and clearly fringed buff (or paler through fading), not broadly fringed grey as described (see Hayman et al 1986 and photo of fresh-plumaged first immature non breeding bird British Birds 70: 217). Quite possibly this discrepancy is age or wear related and does not necessarily go against identification as Caspian Plover. Extent of upperwing-bar: As the observers acknowledge, their description of the upperwing bar does make it sound rather too extensive. However, this is minor discrepancy and available flight photographs (Dutch Birding 5: 44) do suggest that the bar can appear to extend inwards to near the base of the wing, at least on a bird in fresh plumage. Breast and under-body colour and pattern: The upper chest is described as streaked dark grey-brown and mid-chest mottled and abruptly demarcated from an off-white or lightly grey lower chest and belly. Our research shows that Caspian Plover should have a rather broad and uniform grey-brown breast-band. However, the breast-band does look slightly mottled in some photos of birds in non-breeding plumage (e.g. Dutch Birding 5: 40). This feature is an important one in ruling out possible confusion with sand-plovers. Once again the sketch is more reassuring in this respect. Also the off white or slightly grey lower breast should be clean white as far as we can tell from the literature and photos studied. Underwing colour and pattern: Described as off white to white, whitest in half of the wing closest to the body and not contrasting with the belly but contrasting strongly with the chest. This implies that much of the underwing was pale or whitish whereas in reality only the lesser and median coverts are white on a Caspian Plover. The sketch however is reassuring and assisted members greatly in making their decision a positive one. In summary members found this case particularly difficult to assess, however general consensus was that the overall description and particularly the sketch rules out all other contenders and the committee therefore has voted in favour of acceptance. The positive aspects to the submission such as the general size, combination of head and breast pattern, shape of the bill, whitish inner underwing pattern, primary extension ‘just beyond the tail’, short leg length (compared with Pacific Golden Plover) all add up to a positive case for acceptance. It was felt by most members that the variety of anomalies in the fine detail of the submission were (understandably) the result of descriptive technique taken under excited circumstances, rather than grounds for non acceptance. And corroboration in the form of a second experienced observer certainly adds weight to the claim. This record being the first confirmed sighting of a live bird for mainland Australia. The only other Australian reports being a bird from Cocos Keeling (Gibson-Hill 1949) and a specimen of questionably origin from the Northern Territory (Condon 1961). Records of African bound migrants (not only this species) occurring anywhere in Australasia or even Asia are particularly unusual in our opinion.
References and Bibliography
Tony Palliser |