Flyttningsmönster, populationstrender och morfometri hos roskarlar Arenaria interpres vid Ottenby i sydöstra Sverige

Abstract

We analysed 57 years’ uninterrupted trapping data of autumn migrating Ruddy Turnstones Arenaria interpres at Ottenby, south-eastern Sweden (1593 full-grown birds in 1947–2003; of them 574 birds with standardised trapping in 1976–2003). Numbers trapped decreased significantly for both adult and juvenile birds in the total dataset (–0.34 and –0.57 ringed birds per year), and for juveniles in the 1976–2003 dataset (–0.51 per year). Median date for adults was 27 July and for juveniles 6 August. Adult females passed on average three days earlier than adult males (females 27 July, males 30 July). The mean body masses (juveniles 108.0 g, adults 108.4 g) correspond to a fuel load of 21–22% in relation to lean body mass (89 g). Length of stay of retrapped birds was only 3.6 days. Thus, they continued the migration with small to moderate fat loads, comparable to reported fat loads elsewhere. Forty-four recoveries illustrate a narrow migration route along the western coasts of Europe, south to the wintering areas in tropical West Africa.