The presence of a social partner may significantly contribute to coping with stressful events, whereas dyadic separation generally increases glucocorticoid levels and, thereby, might also affect immune function and health. To study the covariation between social factors, immuno-reactive corticosterone metabolites, haematology and parasite product excretion patterns in a free-living, long-term monogamous bird, we separated pair mates in Greylag geese (Anser anser). We isolated the males of eight pairs for 48 hours to examine behavioural, adrenocortical, haematological and parasitological responses to mate removal in the female partners, and to social isolation in the males. Females showed no elevated levels of corticosterone metabolites in their droppings, but their haematocrit decreased during mate removal, whereas leucocyte number and heterophil/lymphocyte (H/L) ratio remained unchanged. In contrast, the socially isolated males excreted significantly elevated levels of corticosterone metabolites compared to baseline and showed a decrease in haematocrit as well as elevated leucocyte number and H/L ratio. In both sexes, the excretion of coccidian oocysts increased within 48 hours of the start of the separation, remained high one week after separation, and returned to baseline four weeks later. Described effects were generally more pronounced in males than in females. Our results suggest relatively swift potential health effects of mate loss and social isolation in an unfamiliar confinement in free-living geese.