Differences in environmental associations of migrants and non-migrants.

We tested whether the average values of the environmental variables differed between migrant and non-migrant populations in the dataset, by fitting a linear model for each variable separately in which it was treated as the dependent variable and migratory tendency as a predictor. Shown is the F-ratio for the model, together with the P-value. For each model we estimated Pagel's ��, and set this equal to its maximum likelihood value. We tested whether this was different from zero and one (respectively as indicated by the superscripts) in order to determine whether significant phylogenetic signal existed (ns = not significant; * = p** = p*** = pTable 2.