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The Measurement of Overall Body Size in Birds
James D. Rising and Keith M. Somers
Vol. 106, No. 4 (Oct., 1989), pp. 666-674
Published by: American Ornithologists' Union
Stable URL: http://www.jstor.org/stable/4087673
Page Count: 9
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We compared a number of univariate and multivariate measures of body size used commonly in ornithological research, including eight multivariate measures (from principal components analyses), plus skull length, ulna length, tibiotarsus length, wing length, and weight. Analyses are based on 26 measurements on three randomly selected male and three randomly selected female Savannah Sparrows (Passerculus sandwichensis) from each of 53 different geographic localities throughout the species' range. Six of the eight principal components analyses provided essentially the same information about body size. Analyses based on the variance-covariance matrix of raw or log-transformed data provided first axes that varied most from the other multivariate estimates of size. Among the univariate measures, ulna length, wing length, and body weight contributed information that diverged from the multivariate measures of overall size. Weight better represents general size (i.e. PC I) than wing length, but because of variation in reproductive condition, weight is a far better measure in males than in females. Wing length is not a representative measure of body size. Inasmuch as each principal components analysis provides information about body size on PC I, we encourage researchers to choose among the various approaches according to analytical objectives rather than methodological simplicity or general utility.
The Auk © 1989 American Ornithologists' Union