Red-necked stint and curlew sandpiper in south-east Tasmania: Part 1 red-necked stint - population trends and juvenile recruitment

• Main Authors: Newman, M, Woehler, EJ
• Format: Article in Journal/Newspaper
• Language: English
• Published: Australasian Wader Studies Group 2016
• Subjects: Biological Sciences; Ecology; Marine and Estuarine Ecology (incl. Marine Ichthyology); Arctic; Austral
• Online Access: http://awsg.org.au/publications/stilt/; http://ecite.utas.edu.au/116913

Red-necked Stint Calidris ruficollis numbers in south-east Tasmania have fluctuated by an order of magnitude during the last 50 years. Current numbers (2010 - 2015) of between 500 and 1000 are at the lower end of the range, which peaked at nearly 4000 between 1981 and 1983. Superimposed on an overall long-term decrease are medium-term fluctuations in the size of summer populations. These fluctuations are similar to those reported in Victoria on the Australian mainland, but the magnitudes of the long-term changes in Tasmania are greater and slightly lagged in time relative to Victoria. The results of banding studies in south-east Tasmania and Victoria provide valuable insights into the overwintering (non-breeding season) behaviour of Red-necked Stints in Australia. In both Tasmania and Victoria, adult birds usually return to the same location each year after breeding in the northern hemisphere. Juveniles do not migrate to breed in the northern hemisphere until at least 18 months of age, although some juveniles undertake a partial movement northward in the Austral winter. Consequently, winter count numbers in Tasmania underestimate annual juvenile recruitment. In Victoria, juvenile proportions of Red-necked Stint in summer cannon net catches have been used to indicate recruitment rates, with annual variations attributed to changes in Arctic breeding success. Similar annual variations are apparent in the proportions of juvenile Red-necked Stint in south-east Tasmanian summer populations, based on the winter / summer count proportions. Between 1980 and 2005, the magnitudes of these metrics were similar during periods when the summer population was increasing, but the Tasmanian proportions were much lower when the populations were decreasing. The results are consistent with a demographic model involving high levels of juvenile recruitment into the south-east Tasmanian population when Red-necked Stint populations are at high levels during summer on the Australian mainland and the juveniles are forced farther south to Tasmania to find foraging opportunities. Short term fluctuations reflect variations in Arctic breeding success, but are variably attenuated by the extent to which juveniles find foraging opportunities at more northern latitudes. Since 2010, south-east Tasmanian results are inconsistent with the previous long-term trends suggesting fundamental change(s) to one or more of the factors affecting the balance between recruitment and mortality may have occurred.