Fig. 4. Water absorption as a function of sucrose assimilation and food intake rate in sunbirds. (A) The volume of water absorbed per mass of sucrose assimilated declined significantly with the sucrose concentration of the diet (r²=0.78; F_1,29=106.66, P<0.0001), despite constant sucrose intake, suggesting that sunbirds regulate transepithelial water flux independently of sugar absorption. (B) The absorbed water load (fractional absorption of ingested water x water intake rate) was positively correlated with food intake rate (r²=0.84; F_1,29=152.53, P<0.0001).