Fig. 5

Species-wise vagrancy likelihood in response to hand-wing index (HWI) and migration distance. Each point represents a different species. Vagrancy likelihood was calculated as the observation frequency offshore divided by the observation frequency on land, normalized with a log transformation. The independent effects of understory foraging preference (a) and HWI, a measure of wing pointedness which correlates to aerodynamic efficiency (b), are shown. The effect of migration distance is shown with its interaction with HWI (c). In birds with a pointed wing shape (high HWI, demonstrated by a Horned Lark wing), the effects of migration distance are reduced. In birds with a rounded wing shape (low HWI, demonstrated by a Wilson’s warbler), longer migration was strongly correlated with increased vagrancy likelihood