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Case Summary for:
Submission No 214: Northern Wheatear Oenanthe oenanthe, Christmas Island, 14 January 1996. (Bird Observer: May 1996 No. 763) Verdict: Not Accepted This case relates to a record of a wheatear sighted in roadside grasslands and vegetation on the North East coast of Christmas Island (105º 42’ E 10º 25’S) on the 14th January 1996. The bird was seen and photographed by several observers over a 45 minute period to a distance estimated to be 15-20m. The submission includes several photographs, a copy of the field notes and a written account of the circumstances behind the sighting. The description and the field notes describe a bird 14-15cm in length with a general medium brown colouration on the head and upperparts. The eyebrow being rather dull and buffy. A largish dark eye and a dark bill were noted with bill estimated to be half the length of the head. Underparts were paler with the breast and belly shading to off white. A faint suggestion of a breast band was apparent. In sunlight the breast band and the throat suggesting a rufous tone. Back colour slightly darker than the head and the wings when folded slightly darker again. The tail was short, however In flight the upper-tail and rump was white with a notable subterminal black band occupying about half the tail length. The photographs although distant validated the description and also revealed a black terminal band to the undertail. The legs were described as longish and black. There were no obvious white outer tail feathers, or any streaking on the bird as a whole. Behavioral notes importantly note the preference for exposed perches and describe the jizz of the bird as having a rather pipit-like stance. The committee has little difficulty in agreeing that this bird is in fact a wheatear Oenanthe spp., the first confirmed record of this genus for Australia. However establishing the specific identity is particularly difficult. As the observers point out, the only real contenders are female and immature plumaged Northern Wheatear O. oenanthe, Isabelline Wheatear O. isabellina and Black-eared Wheatear O. hispanica. Desert Wheatear O. deserti being ruled out by its all black tail. Of the three main contenders, Black-eared appears safely ruled out by the tail pattern: Sketched by the observers as a solid black terminal band uniform in width whereas Black-eared has black tail corners and a black central stem (see text and comparative uppertail patterns in Jonsson 1992, p.398-9). This leaves Northern and Isabelline, a notoriously difficult identification problem that has received a good deal of attention in European literature (see Corso 1997 & Lewington et al. 1991). It is apparent that there is significant overlap in some critical features e.g. tail and supercillium patterns. In particular the upper and underwing patterns are crucial to the identification process. Other more subjective features such as size, body shape, bill shape, leg length and thickness, primary projection etc. are also relevant. The description is (understandably) lacking in detail for all the critical areas and the photographs present an image too small to allow accurate assessment. The upperwing pattern in one photograph does show an obvious contrast between the warm brown upperparts and a comparatively dusky folded wing and this has been suggested as indicative of Northern rather that Isabelline. However the wealth of photographs in Corso (and other papers) demonstrate that such an impression can be shown by both species. Similarly it has also been argued that the relatively narrow dark terminal tail-band is indicative of Northern. No indication is given in the sketch of a dark central stem to the terminal band in the tail, which (again understandably) does place doubt as to the accuracy of the sketch. One of the photographs does suggest a narrow undertail terminal band, however the feature is not shown well and to complicate further considerable variation is possible in both species (Corso 1997). The committee did concur that Northern Wheatear is the far more likely contender when taking into account the likelihood of occurrence given that there are records of this species from Borneo. However, Isabelline and other wheatear spp. have been recorded as vagrants to Japan and all have a proven long-distance vagrancy potential as established by the many vagrant records of this group from the Western Palearctic. Although members were divided in their opinion the committee felt that this record cannot be accepted to specific level, however we have no hesitation in acceptance as a wheatear Oenanthe Sp.
References and Bibliography
Tony Palliser |