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 flight 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 flight display suggests that migration has a larger impact on wing morphology than does flight display, despite the fact that flight display is generally the more heavily used flight-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 flight 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 flight feathers. This exceptionally long flight feather is also found in other genera that perform flight displays.