Variations in leucocyte profiles and plasma biochemistry are related to different aspects of parental investment in male and female Upland geese Chloephaga picta leucoptera

The analysis of plasma biochemistry and haematology to monitor the condition of birds in the wild has been found a useful tool in ecological research. Despite biparental investment in most wild birds studied, some studies of condition indices found sex differences, and attributed these to the costs of egg formation or brooding in females or a higher contribution of males to chick rearing. We studied the natural variation of haematological and plasma biochemistry parameters (namely leucocyte, lymphocyte and heterophil counts, H/L ratio and plasma concentrations of proteins, triglycerides and carotenoids) in relation to the different measures of parental investment in males and females in the Upland goose (Chloephaga picta leucoptera), a socially monogamous species. We found no sex differences in haematological and most plasma biochemistry parameters, but a relation to different aspects of parental investment in breeding male and female Upland geese. H/L ratios were related to body condition and capture date in males while leucocyte counts, plasma protein and plasma carotenoid concentrations varied with clutch measures and hatching date in females. Higher H/L ratios of males in a low body condition and later in the year may reflect stress associated with the investment into the establishment and defence of the breeding territory. Females with higher clutch volumes had lower total leucocyte and lymphocyte numbers and higher levels of plasma protein. Earlier hatching dates were associated with lower numbers of all leucocyte types and higher values of plasma carotenoid concentrations. This indicates that differences in health state are reflected in reproductive performance in female Upland geese. We also found sexual differences in the repeatability of haematological and plasma biochemistry parameters between years and therefore suggest that their potential as a measure of individual quality differs between male and female Upland geese. Finally, numbers of leucocyte counts and plasma triglyceride concentrations of pair partners were significantly related. No study so far investigated these parameters in pair partners and we discuss possible reasons for our finding.