Biometrics of the southern grey shrike lanius meridionalis in relation to age and sex

Abstract

The biometrics of Southern Grey Shrike Lanius meridionalis and differences from the closely related Great Grey Shrike L. excubitor are poorly characterised. The aim of this study was to describe sex and age variation in external biometric measurements for the nominate Southern Grey Shrike L. m. meridionalis in a population from northern Spain. In total, 174 Southern Grey Shrikes were ringed, measured, and sexed by molecular techniques. The overall biometry of the shrikes was summarised by Principal Components Analysis (PCA). There were significant differences in size between sex and age classes. We observed a sexual dimorphism in size, with adult males the largest and yearling females the smallest. According to the PCA, only the first principal component showed significant sex and age differences, and these were related to the tail, wing, third primary, white on primaries and white on rectrices. According to these data, and at least in terms of biometry, the Southern Grey Shrike is more similar to the Loggerhead Shrike L. ludovicianus than to the Great Grey Shrike. © 2007 British Trust for Ornithology.