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Case Summary for:
Submission No 187: Savanna Nightjar Caprimulgus affinis. Christmas Island, 30 May 1994. Unpublished. Submitted by Richard Hill Accepted: 11 August, 1998 This submission relates to a small Nightjar located by spotlight on the edge of the Airport Runway on Christmas Island 30 May 1994. The bird was sitting on the edge of the bitumen and was easily captured by hand, allowing close observation and photographs to be taken prior to release. The bird was measured (total length 215mm) and a few notes taken on the plumage which was described as "a typical Nightjar without white in the tail, and a sub-terminal white flash in the primaries giving a distinct white window in the wing. There was no white on the throat and the chest was barred chestnut and grey". Although the call was not heard the bird uttered a ‘wheezing croak’ when handled. The photographic evidence and the measurements being the key to the positive identification of this case. The committee directed considerable research into the identification of Nightjars from South East Asia and Wallacea in an effort to gain positive identification of this bird and eliminate all possible contenders including those resident in Australasia. Expert opinion was sought from Birdlife International in Indonesia. With Bas Van Balan resolving to accept in favour of Savanna Nightjar C. affinis. A number of Nightjars can be ruled out on size and morphological grounds: White-throated Eurostopodus mysticalis lacks prominent pale spots in outer primaries and lacks broad rusty or rich buff bars in the inner primaries; Spotted Nightjar E. argus has tertials prominently streaked buff and both are too large and normally have much larger white throat patches than this bird. The two New Guinea endemic species, Papuan Nightjar E. papuensis and Archbold’s Nightjar E archboldi both lack white markings in the wing and tail (Coates 1985). The Indian Nightjar C. asiaticus, found as close to Christmas Island as Peninsula Thailand, has white tipped outer rectrices in both sexes (Lekagul & Round 1991). Thoughts are that this bird could have dispersed from nearby land masses such as Sumatra and Java. Possible Nightjar species include Grey C. indicus, Salvadori’s C. pulchellus, Bonaparte’s C. concretus and Savanna C. affinis. Large tailed Nightjar C. macrurus, is ruled out among other features by having prominent white tips to the outermost rectrices and much larger size (Coates 1985). Of the remaining four, Bonaparte’s C. concretus (endemic to Java and Sumatra) has a continuous and prominent white throat patch (MacKinnon & Phillipps 1993) and is also much darker brown on the dorsum. Salvadori’s Nightjar C. pulchellus also endemic to Java and Sumatra is also darker brown above and has white spots or bars in only the two outermost primaries (MacKinnon & Phillipps 1993). This bird clearly showing at least four outer primaries with a prominent pale bar. The Grey or Jungle Nightjar C. indicus, is migratory and might be expected to occasionally overshoot its normal wintering range which extends south to Java and once to New Guinea (Coates 1990). The lack of any white or buff subterminal spots in either the upper or undertail, the paleness of the belly and again the small size helps to rule out Jungle Nightjar C. indicus. Hence we are left with Savanna Nightjar C. affinis as the only possibility. An adult male can be ruled out as this bird lacks the white outer rectrices. All other features are consistent with either an adult female or some intermediate stage between juvenile and adult. The combination of the following characters proving the identification as positive:
The committee accepts this record as the first confirmed for Christmas Island and consequently a new bird for the Australian list.
References and Bibliography
Tony Palliser |