Morphological correlates of migratory distance and flight display in the avian genus Anthus

Conflicting pressures on the evolution of wing morphology are exemplified within the avian genus Anthus, where different migratory and night display behaviours might be expected to exert different effects on the evolution of wing morphology. A phylogenetically controlled study of wing shape in relation to migratory distance and night display suggests that migration has a larger impact on wing morphology than does night display, despite the fact that night display is generally the more heavily used night-type. Correlations between single measures of morphology and migration were found only in males, although principal components analysis suggests that overall wing shape is correlated with migratory distance in both sexes. With regard to night display, males, but not females, show a positive relationship between flight display type and the length of a flight feather that is highly elongated relative to other night feathers. This exceptionally long night feather is also found in other genera that perform night displays. (C) 2001 The Linnean Society of London.