Biometrics and migration of Oystercatchers (Haematopus ostralegus) from the White Sea region (NW Russia)

Biometrics of breeding Oystercatchers were studied in the Kandalaksha Bay (NW White Sea) and existing ringing data of White Sea birds were re‐evaluated to elucidate the position of this isolated NE population. Based on biometrics of known partners, all 58 trapped birds were sexed by discriminant analysis using bill length and body mass; the contribution of wing and tarsus length was insignificant. No clear geographical variation in body mass and wing length could be demonstrated. Kandalaksha birds have significantly shorter (c. 4.5%) legs than Dutch inland (meadow) breeders, which may point to a selective advantage of longer legs in taller vegetation. Bills were all chisel‐shaped (stabbers) and much shorter than in W. Europe. A still speculative explanation is offered in the small size of high‐northern intertidal mussels, the principal prey. Juveniles migrate over a broad front towards Denmark, and then further south. Few birds first return to the White Sea when 2 years old, most are 3 years or older. Cru...