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The Pukeko, or Purple swamphen (Porphyrio porphyrio melanotus), has monomorphic plumage, which makes sexing of the living bird difficult. A method of sexing using body measurements has been proposed (Williams & Miers 1958), but it uses measurements and cut-off values which are not fully reliable. While cut-off values may vary geographically, the reliability of the different measurements should not. This paper uses multivariate techniques to investigate the reliability of combinations of measurements for sexing swamphens and outlines the problems with the existing method.