Migration ecology and morphometrics of two Bar-tailed Godwit populations in Australia
J. R. Wilson A D , S. Nebel B and C. D. T. Minton CA Sandneset, 8380 Ramberg, Norway.
B School of Biological, Earth & Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
C 165 Dalgetty Road, Beaumaris, Vic. 3193, Australia.
D Corresponding author. Email: jimwils@frisurf.no
Emu 107(4) 262-274 https://doi.org/10.1071/MU07026
Submitted: 30 April 2007 Accepted: 3 October 2007 Published: 5 December 2007
Abstract
Bar-tailed Godwits (Limosa lapponica) are long-distance migratory shorebirds. About a third of the global population migrate to Australia during the non-breeding season where they occur mainly in the north-west and east. Using measurements of bill, wing, tarsus and total-head (head and bill), we show that birds from the two main Australian non-breeding regions belong to separate populations. Individuals in north-western Australia are subspecies L. l. menzbieri, which breeds in north-eastern Russia, whereas those in south-eastern Australia are subspecies L. l. baueri, which breeds in northern and western Alaska. Resightings and recoveries of marked birds showed that there is little exchange between the two populations on the non-breeding grounds. They also take different routes during northward migration: L. l. menzbieri was more frequent on staging areas in the western Yellow Sea and largely absent from Japan, whereas L. l. baueri was more numerous in the eastern Yellow Sea and was often recorded in Japan. L. l. baueri left on northward migration 1–2 weeks earlier than L. l. menzbieri and gained more body mass before departure, presumably in preparation for a longer migratory leg. Our data suggest that on northward migration, L. l. menzbieri and L. l. baueri make direct flights of 5400–6200 km and 8200–8500 km, respectively, to reach staging areas in East Asia. The route of Limosa l. menzbieri on its southern passage is similar to that of northward migration, with stop-overs in East Asia. Limosa l. baueri, however, make an ~10 400-km non-stop flight across the Pacific Ocean from Alaska to eastern Australia, one of the longest non-stop migratory flights known amongst birds.
Additional keywords: body mass, Charadriiformes, East Asian-Australasian Flyway, migration routes, shorebirds.
Acknowledgements
The data have been collected by the Australasian Wader Studies Group (AWSG) and the Victorian Wader Study Group over many years, assisted by hundreds of volunteers. They are thanked for countless hours of dedicated fieldwork under often arduous conditions. The efforts of those who have collected and reported flag sightings throughout the Flyway are greatly appreciated. Thanks also to the Australian Bird and Bat Banding Scheme for supplying details of banding recoveries and to the State authorities for providing banding permits. Peter Driscoll and the Queensland Wader Study Group kindly allowed us to use their data. The Australian Government Department of the Environment and Water Resources has provided funding since 2000 to design, compile and manage the flag-sighting database and, more recently, to assist the analysis and publication of data. The AWSG and the Broome Bird Observatory collected and made available the visible migratory departure information. Thanks are also given for comments on drafts of the paper by Mark Barter, Theunis Piersma, Pavel Tomkovich and Doug Watkins and to Mark Barter for help in producing the maps.
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