Size matters: wintering ducks stay longer and use fewer habitats on largest Chinese lakes

Background:Evidence suggests that wintering waterbirds have become conspicuously more concentrated at two largest lakes of the Yangtze River Floodplain,East Dong Ting Lake(Hunan Province,29°20′N,113°E)and Poyang Lake(Jiangxi Province,29°N,116°20′E),relative to other lakes,despite the establishment of reserves elsewhere.While this relationship is likely due to greater extent of undisturbed habitats in larger lakes,we understand little of the drivers affecting individual behaviours behind this tendency.Methods:We tracked wintering movements of three duck species(Eurasian Wigeon Mareca penelope,Falcated Duck M.falcata and Northern Pintail Anas acuta)using GPS transmitters,examining differences between the two largest lakes and other smaller lakes in ducks’habitat use,duration of stay at each lake and the daily distances moved by the tagged birds while at these sites.Results:The Eurasian Wigeon and Falcated Duck stayed five times longer and almost exclusively used natural habitat types at the two large lakes(91‒95%of positions)compared to length of stay time at smaller lakes,where they spent 28‒33 days on average(excluding the capture site)and exploited many more different habitats(including c.50%outside lakes).Conclusions:Our study is the first to show that shorter length of stay and more varied habitat use by ducks at small lakes may contribute to explaining the apparent regional concentration of numbers present of these and other species at the largest lakes in recent years.This compares with their declining abundance at smaller lakes,where habitat loss and degradation has been more manifest than on the larger lakes.

Annual migratory patterns of Far East Greylag Geese(Anser anser rubrirostris)revealed by GPS tracking

Twenty Far East Greylag Geese,Anser anser rubrirostris,were captured and fitted with Global Positioning System/Global System for Mobile Communications(GPS/GSM)loggers to identify breeding and wintering areas,migration routes and stopover sites.Telemetry data for the first time showed linkages between their Yangtze River wintering areas,stopover sites in northeastern China,and breeding/molting grounds in eastern Mongolia and northeast China.10 of the 20 tagged individuals provided sufficient data.They stopped on migration at the Yellow River Estuary,Beidagang Reservoir and Xar Moron River,confirming these areas as being important stopover sites for this population.The median spring migration duration was 33.7 days(individuals started migrating between 25 February and 16 March and completed migrating from 1 to 9 April)compared to 52.7 days in autumn(26 September-13 October until 4 November-11 December).The median stopover duration was 31.1 and 51.3 days and the median speed of travel was 62.6 and 47.9 km/day for spring and autumn migration,respectively.The significant differences between spring and autumn migration on the migration duration,the stopover duration and the migration speed confirmed that tagged adult Greylag Geese traveled faster in spring than autumn,supporting the hypothesis that they should be more time-limited during spring migration.