Figure 2.

(a) The effect of natural variation in individuals' provisioning rates on their body mass at peak provisioning. Birds provisioning at a higher rate subsequently had a significantly lower body mass at peak provisioning, while controlling for the effects of individual variation in body mass at clutch completion and dominance/sex status (see Results). The solid line represents the prediction from a mixed effects model containing clutch completion mass and provisioning rate as predictors, and social group ID as the random effect. The predictions are for an individual of mean clutch completion body mass (44.66 g—indicated by the dotted line) and the points represent residuals from this model (n = 24 birds from 11 social groups). (b) The effect of natural variation in individuals' provisioning rates on their plasma residual TAC at peak provisioning. Birds provisioning at a higher rate subsequently had lower plasma residual TAC. The diagonal solid line represents the model predictions from a mixed effects model in which provisioning rate was the only predictor and social group ID the only random effect, and the points represent residuals from this model (n = 39 birds from 15 social groups).