Fig. 5. The ¹⁵N of cells, plasma and excreta was significantly enriched relative to diet in Yellow-vented bulbuls on all diets. In contrast, the ¹⁵N of urine was depleted relative to diet in birds fed the diet with the low protein content. The ¹⁵N of urine did not differ from that of diet in birds fed the diets with the medium and high protein content. Error bars represent 95% confidence intervals for means.