Stopover strategy of adult and juvenile Red Knots Calidris c. canutus in the Puck Bay, southern Baltic

Abstract

For Red Knots Calidris c. canutus sandy coasts of the southern Baltic seem to be a low quality stopover site, because of unpredictable feeding conditions and a low density of molluscs. Observation collected in the Puck Bay, Poland, suggest that Knots feed mainly on Nereis sp., Gammarus sp., small sized Hydrobia sp. and small insects taken from wet sand. Among 1471 Knots ringed 27.8% of juveniles and 10.5% of adults were retrapped few days after the first capture, which indicates that the majority had a short stay and apparently departed with small energetic reserves. In spite of poor feeding conditions the fuel deposition rate of the Knots in autumn (adults: 2.4 g per d, juveniles: 2.7 g per d) was similar to that observed in the Dutch Wadden Sea and the Baltic coast of SE Sweden. It is suggested that Knots are able to accumulate body stores despite low food quality and density because the lack of tides allow them to forage without interruption, and because there is no additional energetic cost related to increasing gizzard size.