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Continental Patterns of Morphological Variation in a South American Sparrow

Paul Handford
Evolution
Vol. 37, No. 5 (Sep., 1983), pp. 920-930
DOI: 10.2307/2408407
Stable URL: http://www.jstor.org/stable/2408407
Page Count: 11
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Continental Patterns of Morphological Variation in a South American Sparrow
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Abstract

Geographic variation in bill, leg, foot and wing characters is described in Zonotrichia capensis, the South American Rufous-collared sparrow The species ranges from southern Mexico throughout all of South America and the 1,554 specimens effectively cover the entire range. The major findings are as follows. The sexes differ strongly in size yet their geographical variation in shape is virtually identical. There is no clear relationship of intrapopulation variability with latitude. Several characters show latitudinal clines (especially if only the Andean region is considered) which reverse across the tropical zone. The longest and (in terms of volume) the largest bills are found in the tropics; the shortest and smallest in Patagonia, a pattern which perhaps relates to mean food particle size. The longest wings (both in absolute and relative terms) are found in temperate high altitudes and at high latitudes. This is interpreted as a reflection of a migratory/nomadic habit.

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