Figure 1. Dive depths of South Georgia Shags in relation to sex, ranked body mass and trip-within-individual variation.

Squares represent females and circles males. The large symbols indicate the average dive depth by an individual and the small symbols the average by each trip it made, taken from the fitted values of the selected model. Dotted lines indicate the average dive depths for females (19.4 m) and males (42.7 m). The solid line represents the best-fit regression of dive depth against mass from the model without sex included (equation of the line, depth = -82.7 + 47.7 x mass (kg)), note that the plotted slope is irregular as mass is on a ranked scale to prevent overlap of points for individuals such that mass increments across tick intervals are variable.