Figure 2.

Relationship between nestling PC1 index and body skin UV chroma. PC1 index is the first principal component of a principal component analysis, with body mass and skeletal size as loading factors. High PC1 index indicates that offspring were large and heavy for their age. (a) Alpine swift nestlings issued from reduced and enlarged broods (closed and open symbols, respectively). (b) European starling nestlings issued from first broods (closed symbols and dashed line) and second broods (open symbols and solid line).