Memorandum to: The Director of Birds Australia
From: Birds Australia Rarities Committee (BARC)
Date: 13th
February 200817th
January 2008
Voting Members: Jamie Matthew Danny Rogers
Glenn Holmes Rohan Clarke
John Hatch Tony Palliser
Andrew Silcocks David Bishop
cc: Ron Johnstone, Peter Lansley
Submission No 493: Grey Nightjar Caprimulgus indicus, Timor Sea, 23rd August 2005
This case relates to a Caprimulgus Nightjar photographed by a non-birder sitting on the rail of the ship the ‘Southern Supporter’ in northern Australian waters (11º56’S 125º00’E) on the 23 August 2005. The photograph passed through three intermediaries before being handed to the submitter. This resulted in some important information such as the dimensions of the rail on which the bird was sitting not being available.
As pointed out by the submitter it is immediately apparent that the photographed bird is not one of the regularly occurring Australian Nightjars, White-throated Eurostopdus mystacalis, Spotted E. argus or Large-tailed C. macrurus. All have strongly marked white throat patches absent in this bird. Various other structural and plumage features also combine to eliminate those species. Other Nightjars of the region, Heinrich’s, E. diabolicus, Great Eared E. macrotis and Sulawesi C. celebensis, are very distinct and can be eliminated immediately.
A careful diagnosis comparing the photograph with illustrations was presented to the committee. This analysed subspecific distinctions, age and sexual differences and comfortably eliminated all contenders other than Grey and Savanna Nightjar. Features noted within the submission that suggest Grey Nightjar rather than Savanna include a narrow white sub-moustachial streak, bold streaks on the scapulars, pale spots on the wing-coverts and a slightly longer primary projection.
The first round of voting indicated just how difficult this case was with one member voting against acceptance and most indicating that they would prefer expert consultation. The photograph provided was good but nightjars are difficult to identify on the basis of photographs. Consequently, the committee approached three experts. One failed to respond; one said he found the problem too difficult and the other, Peter Lansley, who has extensive experience in the field in Indonesia, offered the following opinion.
“Due to the variability of plumages of the Caprimulgus nightjars which may occur in Australia, this is a complex case. Of two previously recorded as vagrants to Australian territory, one, the Savanna Nightjar, has 10 recognised subspecies and the Grey Nightjar has five (del Hoyo et al. 1999). There is a lack of, or conflicting, detail in several regional field guides regarding key identification features particularly those relating to the finer details of plumage.
As stated in the submission, the bird is clearly a Caprimulgus Nightjar since it possesses rictal bristles. This rules out members of the genus Eurostopdus as these lack this feature. The Australian resident Large-tailed Nightjar C. macrurus is also ruled out by the lack of a white throat patch and the tip of the wing reaching only just short of end of the tail. Other species in the general south-east Asian region or migratory forms from north-east Asia that might reach Australia can be ruled out: Bonaparte’s Nightjar C. concretus lacks a white flash in the primaries (del Hoyo et al. 1999). Salvadori’s Nightjar C. pulchellus lacks pale (whitish) spotting in the wing coverts according to illustrations and text in del Hoyo et al. (1999). The latter two species are in any case endemic forest birds extremely unlikely to ever occur naturally in Australia. Philippine Nightjar C. manillensis and Sulawesi Nightjar C. celebensis are similar to Large-tailed Nightjar in their plumages (del Hoyo et al.1999) and ruled out on much the same basis. Eurasian Nightjar C. europaeus has longitudinal streaking on the crown, nape and scapulars (Grimmett et al. 1999), which are not present in the subject bird; Indian Nightjar C. asiaticus has a rufous nuchal collar (Grimmett et al. 1999) lacking in the subject bird.
The primary projection beyond the tertials, expressed as a proportion of wing length has been put forward as a character useful in separating Grey and Savanna Nightjars. Examination of photographs downloaded from the Oriental Bird Images Database indicate that the primary projection in Grey Nightjar may vary from 30 to 36 % of wing length (n=10), but is usually around 31-33% of wing length (5 of 10). In another photograph of Grey Nightjar (Kanouchi et al. 1998), I estimated primary projection at 30% and 28% of wing length respectively for two birds in which the entire wing was visible. Two birds in Iozawa et al. (2000) were estimated at 31% and 30% for male and female respectively. One of P. Ford’s photographs of the first Australian Grey Nightjar had a proportion of 31.5%. Taking images of eastern subspecies of Savanna Nightjar from Oriental Bird Images Database (n=5), i.e. excluding those of C. a. monticolus from the Indian subcontinent, primary projection varied from to 24 to 28%. I estimated a proportion of 25.9% from a published photograph of Savanna Nightjar in Strange (2000).
My estimate of the primary projection of the Timor Sea nightjar of this submission is 26.5% of wing length (and that of Danny Rogers, 27.5%) and therefore it falls within the range of values more typical of Savanna rather than Grey. I disagree with the proportion quoted in the submission and believe the wing has been measured incorrectly. Some feathers seem to be fluffed out by the breeze – these may have been taken as the front end of the wing.
It would seem that on photographic data available to me, birds with primary projection proportions lower than 28% can be assigned to affinis, whereas those over 30% can be regarded as indicus. This compares to the figures attributed to John Darnell of the WA Museum in the submission that this proportion in Savanna varies from 26 – 28.5% and that in Grey it varies from 31 – 35.5%. It would be useful to have confirmation of this feature by publication of measurements of museum skins and birds in the hand, but certainly this structural feature casts doubt over the identification of Grey Nightjar in this case.
The submoustachial stripe is mentioned in the submission as supporting the case for Grey Nightjar. I disagree. Several photographs of Savanna I examined [eastern subspecies from Java, Singapore, The Philippines and Hong Kong] from Oriental Bird Images database and Strange [2000]) showed Savanna with a distinct pale submoustachial stripe. Del Hoyo et al (1999) also show this for the nominate form from southern Indonesia. The subject bird could therefore be within the range of variation of Savanna Nightjar for this feature, especially given the bright light in which it has been photographed.
The pale spots on the wing coverts are not too far removed from the illustration of male Savanna of nominate subspecies in del Hoyo et al (1999). This form is found as close to Australian as Lombok. Care must be exercised in interpreting the photograph since it has clearly been taken in bright light.
The scapulars are difficult to make out clearly in the subject bird and don’t really help one way or the other.
Finally, as pointed out in a contra-indication in the submission, the lesser coverts appear to be too pale for a Grey Nightjar. I agree, and this is a clear point of difference with photographs by P. Ford of the first accepted Grey Nightjar.
Based on all the above lines of evidence, I don’t think the case is sufficiently made out to accept this bird as a Grey Nightjar Caprimulgus indicus. Sexing and ageing are also difficult to resolve because no white is visible in the tail yet white is present in the primaries”.
This content resulted in a unanimous “non acceptance” on the second round of voting. To date there has been only one record of Grey Nightjar for Australia (see BARC Case No. 450). This is a case where a specimen or at least a bird in the hand is absolutely necessary. The committee would like to take this opportunity to sincerely thank Peter Lansley for his invaluable opinion.
·
Christidis,
L. & Boles, W. E. (1994), The Taxonomy
and Species of Birds of Australia and its Territories, RAOU
Monograph 2, Royal Australasian Ornithologists Union, Melbourne.
Cleere, N. & Nurney, D. (1998), Nightjars,
Pica, Sussex.
· Coates, B.J. (1990), The Birds of Papua New Guinea, Vol. 2, Dove, Alderley, Queensland.
· Coates, B.J., Bishop, K.D. & Gardner, D. (1997), A Guide to the Birds of Wallacea, Dove, Alderley, Queensland.
· Cramp, S. (Ed.) (1985), The Birds of the Western Palearctic, Vol. 4, Terns to Woodpeckers, Oxford University Press, Oxford.
· Grimmett, R., Inskipp, C. & Inskipp, T. (1998), Birds of the Indian Subcontinent, Christopher Helm, London.
· Iozawa, H., Yamagata, N. & Yoshino, T. (2000), Japanese Bird 550: Landbirds, Bunichi General Publisher, Tokyo (in Japanese).
· Kanouchi, T., Abe, N. & Ueda, H. (1998), Wild Birds of Japan, Yama-Kei, Tokyo (in Japanese).
· MacKinnon, J. & Phillipps, K. (1993), A Field Guide to the Birds of Borneo, Sumatra, Java and Bali, Oxford University Press, Oxford.
· Robson, C. (2000), A Field Guide to the Birds of South-East Asia, New Holland, London.
· Strange, M. (2000), A Photographic Guide to the Birds of Southeast Asia, Periplus Editions, Hong Kong.
· Wild Bird Society of Japan, (1982), A Field Guide to the Birds of Japan, Wild Bird Society of Japan, Tokyo.
Tony Palliser
Chairman Birds Australia Rarities Committee (BARC)