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.
Highlights
Waders have been a focal group for many ornithological studies, because of their spectacular migrations and fascinating behavioural adaptations (Piersma et al 1996)
The present paper is one of four recent ones analysing the migration of waders at Ottenby Bird Observatory, south-eastern Sweden (Waldenström & Lindström 2001, Blomqvist et al 2002, Hedenström 2004)
Long-term population trends The number of birds ringed during one autumn varied between 0 (1968 and 2002) and 129 (1953), with an average of 27.9 (Figure 1)
Summary
Waders have been a focal group for many ornithological studies, because of their spectacular migrations and fascinating behavioural adaptations (Piersma et al 1996). To correctly assess long-term trends, especially for the less common species, there is an urgent need for quantitative datasets covering many years. At Ottenby, trapping of waders for ringing has been carried out since 1946, in a small area and with nearly the same trapping effort over the years. This material enables analysis of population trends in several species of waders, as well as detailed studies on migratory strategies and the timing of migration
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