Parent Kittiwakes experience a decrease in cell-mediated immunity as they breed

The maintenance of an effective immune system may entail physiological costs only affordable by individuals in good condition. Some species, like Black-legged Kittiwakes (Rissa tridactyla) in the high arctic, experience important physiological changes during breeding in order to fulfil their reproductive goals. We studied the effects of breeding effort on the cell-mediated immunity (CMI) of adult breeding Kittiwakes. Parent Kittiwakes showed a significant decrease in CMI from hatching to 15 days into the chick-rearing period, when both parents are known to experience a drastic increase in energy expenditure together with important physiological adjustments. Despite being a long-lived species with biparental care, parent Kittiwakes at the northern border of their breeding range, seem to experience important reproductive immunosupression, even during favourable breeding years.