Biometrics and body mass variation of Curlew Sandpiper Calidris ferruginea caught on the Puck Bay coast, Poland, during southward migration

The study was conducted on the Puck Bay coast (inner part of the Gulf of Gdan´sk, Polish Baltic coast). Between 1983 and 1998, 1783 Curlew Sandpipers were trapped in walk-in traps and measured. The absolute differences in the average measurements between adults and juveniles were small. Nonetheless, all measurements of adults (except tarsus length) were significantly longer than in juveniles. In adults, only the distribution of bill length showed bimodality, whereas in juveniles, two peaks appeared only in wing-length distribution. In juveniles, the average wing length, the total head length and tarsus length varied significantly between years.

Within a season, 158 (19.3%) juveniles and 47 (4.9%) adults were trapped more than once. The median length of stay of adults was two days, while that of juveniles was four days. On average, during the first three days after initial capture, juveniles put on 3.8 g and adults 5.2 g. Birds that did not increase body mass during the first days after catching had significantly higher body mass at first capture than birds that put on weight from the beginning. The highest rate of body mass increase occurred at the beginning of the staging period and later on its value decreased gradually. The mean body mass of birds caught in Puck Bay was low in comparison to data collected during southward migration in other parts of Europe. This suggests that Curlew Sandpipers migrate through Puck Bay with small fat reserves.