Sexual dimorphism in size and plumage in adult Curlew Sandpipers (Calidris ferruginea) migrating in autumn through the Baltic Sea region

Abstract

The Curlew Sandpiper (Calidris ferruginea) displays sexual dimorphism in size and in breeding plumage. We analysed biometric and plumage characteristics in adult Curlew Sandpipers and proposed a protocol for sexing individuals, with the use of the discriminant function analysis. We measured 222 females and 164 males captured during autumn migration on the southern Baltic coast, among which 92 females and 84 males were photographed for analysis of plumage characteristics. All birds were sexed with molecular methods. Females were larger than males in all body measurements. Bill length was the most dimorphic trait, and the most effective function with bill length as a single predictor correctly identified the sex of 82.1% of birds.