Morphometric variation in Indian samples of the Common Myna, Acridotheres tristis (Aves: Sturnidae)

Morphometric variation in 9 characters of 347 Common Mynas from 10 localities in India was analysed statistically. Both sexes have differentiated similarly among localities in all characters. Character variability within localities is not significantly correlated with that among localities. The patterns of geographic variation are not clinally ordered; contiguous localities often are not most similar morphometrically. Size variation, as represented multivariately by principal factor I, is not related linearly to corresponding environmental variation among localities. However, relative appendage proportions, as defined by principal factor II, regresses significantly on an altitude factor for both males and females. The comparatively small proportion of the total morphometric variation among localities accounted for by environmental variation suggests that other factors are operative in determining body size. It is speculated that geographic variation in interspecific competition and food particle size may also act as selective pressures in the evolution of optimal body size at each locality.