Fig. 2.

Principal Components Analysis (PCA) with morphological data per species A) Red-billed Chough, B) Common/Canary Islands Chaffinch, C) Dark-eyed/island Junco, D) House Finch. The variables included are wing, tail and tarsus length and bill culmen, bill depth, bill width and bill length (the latter is not included for the Red-billed Chough). The correlation circle with radius 1 show the loadings of each variable that are represented by the arrows. Red and blue markers correspond to insular and mainland individuals, respectively