Fig. 3. Dietary protein content had a significant effect on the average residence time of ¹⁵N in the plasma solutes and blood cells of Yellow-vented bulbuls. Columns denote means and bars s.e.m. Means with the same letter in each panel are not statistically different from each other. We plotted the data on plasma and cells using the same scale to emphasize the large difference in incorporation rate, and hence residence time, between these two tissues.