SEX DETERMINATION OF ANTARCTIC PETRELS THALASSOICA-ANTARCTICA BY DISCRIMINANT-ANALYSIS OF MORPHOMETRIC CHARACTERS

We present data on sexual dimorphism in some morphological measurement s (wing length, head length, bill depth and bill length) in the Antarc tic Petrel Thalassoica antarctica. Males were on average larger than f emales for all measurements. Sexual dimorphism was on average largest for bill depths whereas wing lengths discriminated least between the s exes. A discriminant function including bill depth, head length and wi ng length correctly sexed 92% of the sample. Due to between-measurer v ariation it is recommended that morphometric measurements obtained by others on sexed birds are compared with ours before proceeding with th e use of the discriminant function on unsexed individuals.