Fig. 3. Sensitivity analysis of rainfall-related increases in activity costs, adjusted for possible external water mass, in captive dunlin under ad libitum feeding conditions. Difference in activity cost = costs on days with rain – costs on days without rain. Gross utilization efficiency = assimilation efficiency x efficiency of utilization of metabolizable energy. Solid lines indicate varying energy density of stored body tissue, labeled as the proportion of mass that is fat; dotted lines indicate lower 95 % confidence intervals for each energy density.