WING-SHAPE VARIATION BETWEEN RESIDENT AND TRANSIENT WINTERING SISKINSCARDUELIS-SPINUS

Pointed wings allow faster, more energy-efficient flight, and so are t hought to be an adaptation for migratory movements. Here we compare wi ng-shape variation between Siskins Carduelis spinus that either remain in a single wintering area (residents) or move continually throughout the winter (transients). Wing shape was computed using the PCA techni que of Chandler and Mulvihill (1988). We develop, however, a statistic al modification that controls for allometric effects on body shape, al lowing a size-independent interpretation of the data. Transients showe d shorter proximal primary lengths (Principal Component 1) than reside nts, so that their wing was more pointed than that of resident birds. Since both winter-resident and transient Siskins are migratory, differ ent strategies in the use of the same wintering area have apparently b een sufficient to select for a different wing shape. Given the heritab ility of several body size variables, the difference in wing shape rep orted here suggests that there has been parallel evolution of morpholo gical and behavioural adaptations to either a nomadic or a winter-resi dent lifestyle.