Geolocator studies on Ruddy Turnstones Arenaria interpres and Greater Sandplovers Charadrius leschenaultii in the East Asian-Australasia Flyway reveal widely different migration strategies

In 2010, following successful trials with geolocators on Ruddy Turnstones in 2009, a total of 105 units, of four different models, were deployed at five locations on Ruddy Turnstones and Greater Sandplovers. Geolocator retrieval rates were 44% on Ruddy Turnstone and 27% on Greater Sandplover. Complete (59%) and partial (15%) technical failure rates on geolocators were high and were mostly the result of wear and saltwater corrosion. All 30 units from the Swiss Ornithological Institute failed. Only half of the Mk10 and Mk12 units from the British Antarctic Survey produced full migration histories. The northward migration of Ruddy Turnstones was on a narrow path with many birds completing an initial non-stop flight of 7,600 km to Taiwan. Later, most made a stopover in the Yellow Sea. Median migration duration was 39.5 days and average migration speed of the first major leg of the journey (assuming the birds followed the great circle route between stopovers) was 63.4 kph. Southward migration paths showed a much wider spread, ranging from Mongolia to the central Pacific. The latter involved the same bird that had been tracked along this route the previous year. It has now been logged on similar 27,000 km round trips in two successive years. The median duration of southward migration (78 days) was nearly twice that of northward migration and data on average migration speed for just two migration legs indicated that it might be lower, 30 and 40 kph being the values recorded. Greater Sandplovers were only tracked on northward migration but seemed to follow a similar migration strategy with a large initial non-stop flight followed by shorter flights and more regular stopovers. Plans are outlined for further analyses and future deployments of geolocators.