Migration patterns and morphometrics of Common Sandpipers Actitis hypoleucos at Ottenby, southeastern Sweden

Abstract

Current knowledge of the migration of the Common Sandpiper Actitis hypoleucos is still limited. The species has been ringed at Ottenby Bird Observatory, southeast Sweden, since 1947, allowing for analyses of long-term and seasonal trends. We analysed trapping data for 1,942 adults and 3,290 juveniles with respect to patterns in phenology, morphometrics, and fuel load. We used fuel loads to estimate potential flight ranges. The number of adult birds trapped increased significantly over the years, whereas juveniles declined. Median passage date was 27 July and 7 August for adult and juvenile birds respectively, and juveniles showed a significant advancement in median passage date. Mean fuel loads were 28.8% and 27.8% of lean body mass (LBM) for adult and juvenile birds respectively, while maximum fuel load was as high as 98.7% in juveniles and 105.4% in adults. Fuel load increased significantly with date in juveniles but declined in adults. Advancement in passage of juvenile birds over the year is possibly due to climate change. Also, the average adult and juvenile are theoretically capable of a direct flight to central France; a major recovery area. Fuel load patterns suggest that in autumn, the two age classes use different migration strategies.