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Case Summary for:
Submission No 195: Short-billed Dowitcher Limnodromus griseus, Corner Inlet, VIC. 18th June 1995. Submitted by C. Minton Verdict: Accepted This record relates to a bird submitted initially as a Long-billed Dowitcher Limnodromus scolopaceus after being captured as part of a wader banding exercise conducted by the Victorian Wader Study Group at Barry Beach, Corner Inlet, Victoria in June 1995. The bird was examined closely, measured, photographed, banded and then released. On examination in the hand it quickly became apparent that the bird was either a Long-billed or Short-billed Dowitcher L. griseus, thereafter attention was concentrated on differences which might be useful in distinguishing between the two species. The description that was written in the field along with photographs were then presented to the committee as a very well documented case for review. The bird described was accurately considered to be an adult basic (winter) plumaged individual with the dorsal photographs appearing to show two generations of feathers of non-breeding pattern and there was no sign of any juvenile plumage in the wing. Based on knowledge available the originators then went on to explain the reasons for believing this bird to be L. scolopaceus detailing the extent of white barring on the tail, markings and colouration of the upper breast, under-tail covert barring and importantly the biometric measurements. The final conclusion being that the combination of plumage, measurements and probability of occurrence all point towards the bird being a Long-billed Dowitcher. Key measurements taken include: Total head length 87.7mm, Bill length 58.2mm, Wing length (Maximum chord) 155mm, Tarsus 37.3mm and Weight 114g. After the first round of voting, much discussion and review the committee came to the conclusion that a basic plumaged individual such as this would require expert opinion. Consequently we approached Joe Morlan of the Californian Bird Records Committee for assistance who because of the complexity of the case also enlisted Alvaro Jaramillo who is an authority on this identification having written two papers on the subject (Jaramillo et al 1991). The resulting opinion was a professionally written recommendation that jointly concluded that this bird is unacceptable as a Long-billed Dowitcher and that it is actually a Short-billed Dowitcher. The opinion provided was very informative and completely convincing offering an explanation of the features and views presented as part of the original submission of Long-billed Dowitcher. It was pointed out that that the tail pattern in Long-billed always has broad dark bars and narrow white ones while Short-billed is highly variable. The corner inlet bird did not have a mainly white tail, and its tail pattern therefore fell into the range of variation shared by Long-billed and some Short-billed Dowitchers. Otherwise there are no known reliable plumage characters which separate these two species in basic plumage. In North America field identification in basic plumage is determined only by call. Long-billed tends to be the more vocal of the two. The breast pattern is unreliable and difficult to assess in the field. In general Long-billed is smoother and darker, short-billed is paler and more spotted, but many birds present intermediate appearance (Pitelka). It was felt that the small darker brown spots on the breast of the Barry Beach bird was suggestive of Short-billed, but this cannot be relied upon for positive identification. Measurements were in fact the best criteria for identifying this bird. Both Jaramillo and Morlan agreed that the measurements point straight to Short-billed and eliminate Long-billed. Critical measurements are wing and bill length. Even when corrections for differences in measuring techniques and shrinkage are taken into account, the Corner Inlet wing length of 155mm is barely within the wing length range of the largest adult female Long-billed among the hundreds of specimens measured by Pitelka. But the culmen of 58.2mm is well below the minimum of 65.5mm for adult female Long-billed in Pitelka’s sample. So the bird just does not measure out as a Long-billed unless you identify it as a female on wing-length and a male on bill-length. However, both wing and bill measurements fit female Short-billed Dowitcher of the race L.g.caurinus. The wing is too long for a male but well within the range of 142-157mm for adult females and the bill fits nicely within the range of 56.8-68.5mm for adult female Short-billed. L.g.caurinus was described by Pitelka as the largest subspecies of Short-billed Dowitcher, which is the race which breeds in Alaska. It was also pointed out by Jaramillo and Morlan that there was a misconception that Long-billed Dowitcher is the more likely to occur in Australia because of its longer distance migration. In fact Short-billed Dowitcher is the longer distant migrant and is the only one of the two which has been unequivocally recorded from Southern South America. There are also records of Short-billed Dowitcher from Japan, although Long-billed Dowitcher is more common there, so there is a precedent for Short-billed Dowitcher migrating down the wrong side of the Pacific Ocean. Once there, Short-billed is far more likely to migrate south of the equator. After a second and final round of voting the committee agreed unanimously with the expert opinion voting in favour of Short-billed Dowitcher as a new species for Australia without reservation. We would like to take this opportunity to congratulate the originators for providing the committee with such well documented and thorough presentation and both Joe Morlan and Alvaro Jaramillo for providing such an invaluable expert opinion. It is unfortunate that some authorities (e.g Pizzey 1997) have proceeded with publication as "confirmed Long-billed Dowitcher" prior to this formal result by the committee.
References and Bibliography
Tony Palliser |