MORPHOMETRICS AND SEXING OF THE AFRICAN BLACK OYSTERCATCHER

Abstract

Summary Hockey, P. A. R. 1981. Morphometries and sexing of the African Black Oystercatcher. Ostrich 52: 244–247. 109 African Black Oystercatchers Haematopus moquini were caught, measured and sexed by cloacal examination during the 1979/1980 breeding season. Six standard taxonomic variables were measured. Females were larger than males in all dimensions considered. The most dimorphic characters were mass and exposed culmen length. The data were subjected to stepwise discriminant analysis and a linear function was derived which allowed birds of unknown sex to be sexed. The function is D = −0,391x1 −0,016 x2 +0,218 x3 +0,714 x4 +15,946 where x1 = exposed culmen length (mm), x2 = body mass (g), x3 = length of tarsometatarsus (mm) and x4 = culmen depth at the gonys. Values of D from the above equation less than zero indicate a female while those greater than zero indicate a male. The greater the divergence of D from zero, the higher the probability of correctly sexing an unknown individual: once D> ± 1,2, p>0,99.