Sex- and age-related variation in plasma carotenoids despite a constant diet in the Red-legged Partridge Alectoris rufa

We studied seasonal variation in plasma carotenoid levels of captive Redlegged Partridges Alectoris rufa in relation to sex, age and condition. The legs, bill and eye lores in this species are bright red due to carotenoid pigments. Carotenoid levels in the plasma varied significantly among sampling periods. Males presented higher values than females of their same age group, except in the last sampling period in summer. Adult partridges (2-year old) presented significantly higher carotenoid levels than first-year birds at the beginning of the study, but this age effect was not constant throughout the season. The sex-specific variation in plasma carotenoids cannot be attributed to diet, as this was the same for all individuals across the study. Body mass, and thus condition, did not change significantly across the study, and was therefore not related to seasonal variation in plasma carotenoids. These results imply physiological regulation of carotenoids, opposite to a direct relationship among carotenoid content in the diet and colour expression in the integument, as suggested in some previous studies

Negro J.J., Tella J.L., Hiraldo F., Bortolotti G.R. & Prieto P., ARDEA 89 (2): 275-280