Variation in the size and shape of introduced starlings, Sturnus vulgaris (Aves: Sturninae), in New Zealand

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Abstract
Starlings were introduced into New Zealand from Great Britain [UK] between 1860 and 1880. Substantial numbers of birds, released at many points in the country, have given rise to populations now occurring throughout New Zealand. Morphometric variation in 16 characters, including 8 derived size and shape variables, was assessed statistically in 8 samples totalling 384 adults. Univariate analyses revealed that all 16 characters of males but only 9 of females varied significantly among localities. Discriminant analysis confirmed that character variation was essentially haphazard among localities. The degree of sexual dimorphism did not covary with latitude. Both among and within localities, a 3-dimensional shape vector, involving bill length, tail length and middle toe length, was associated with many linear size variables, but not with overall size as represented by the geometric mean of external characters or with body weight. The size of females was more closely aligned with environmental variables than was size of males, but males showed a greater association between interlocality and intralocality character variability. The greatest differences between the sexes was in geographic variation of bill size and shape, suggesting intersexual ecological differentiation.