Fig. 2. Effects of carotenoid supplementation and immune challenge on physiological parameters of greenfinches. For carotenoids, individual changes are tested with Wilcoxon matched-pairs tests and between-treatment differences with Mann-Whitney U-tests. Carotenoid concentrations, marked with different letters, are significantly different from each other (P<0.05). Group sizes range from five to eight on the first-titre measurement and from 11 to 14 on other occasions. Mean-trait values, exact sample sizes and statistics are presented in Table 1. For other variables, P-values for time x treatment interaction terms are presented in the text, and in most cases each group contains 14 individuals. Open squares, carotenoid-saline; filled squares, carotenoid-SRBC; filled circles, water-SRBC; open circles, water-saline.