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Case Summary for:
Submission No 210: Variable Oystercatcher Himantopus unicolor, North Stradbroke Island, QLD, 16th March 1996. Verdict: Not Accepted An interesting submission comprised of an excellent set of notes and sketches taken in the field. These notes clearly describe an oystercatcher fitting the general appearance of H unicolor and baring a metal band on its left tarsus. Detail describes black upperparts, head, neck and breast, with scattered white feathers on the lower breast grading to an almost clean white belly. The lower flanks are described as being mottled with white. Pied Oystercatcher H. longirostris is ruled out by the extent of black on the breast and belly and the lack of a vertical white shoulder mark. Sooty Oystercatcher H. fuliginosus is ruled out by the presence of white on the belly and flanks. As pointed out by the claimant, the main identification problem lies in ruling out a hybrid longirostris x fuliginosus as an explanation for the appearance of the bird under consideration. Indeed, hybridisation between these two species is not unknown and there are several reliable though as yet unpublished records in Australia of odd-plumaged oystercatchers considered to involve hybrids of these species. One committee member commented that he has sighted an apparent hybrid oystercatcher in Victoria that also fits the description of the bird under consideration. We also note that H. unicolor is considered to be a short distant migrant at best in New Zealand (see HANZAB Volume 2 for details) and is therefore rather unlikely to occur as a vagrant as far away as Queensland. In summary the Committee feels that because a hybrid origin has not been ruled out, the identity of the bird as H. unicolor has not been established beyond all reasonable doubt. Examination of the bird in the hand may well be the only way to positively establish its identity. As this is not practicable there is little more that can be done at this time and we find against acceptance of this record. The committee encourages the observer to publish his observations so as to highlight this little-known identification problem.
References and Bibliography
Tony Palliser |