Sex Identification of Jack SnipeLymnocryptes minimusby Discriminant Analysis of Morphometric Measurements

Abstract

Jack Snipe Lymnocryptes minimus is a small wader showing sexual monomorphism in plumage and some dimorphism in size. To study whether parameters of body size may be used to reliably sex individuals of this species, a discriminant function analysis was applied to a set of morphometric traits measured in birds caught during migration and the wintering period in northern Poland. Birds were sexed molecularly based on size differences in CHD-linked sequences from W- and Z-chromosomes. Males were significantly larger than females in wing length, head length, skull length, bill depth, bill width and the length of middle toe with claw, while females had longer bills. All traits except for bill width were highly repeatable. A stepwise discriminant function analysis selected wing length, skull length, bill length and bill depth as the best discriminators of sex in Jack Snipe. The discriminant function based on these four traits enabled reliable sexing of 99% of individuals. The alternative function, excluding wing length, which may not always be available for measurement, showed 96.7% classification success. Such very high success in sex identification by a discriminant analysis of morphometric traits may promote this approach as an alternative to molecular sexing techniques in Jack Snipe, when non-invasive sampling is required.