  Immunity is believed to share limited resources with other physiological
functions and this may partly account for the fitness costs of reproduction.
Previous studies have shown that the acquired immunity of female common eiders
(Somateria mollissima) is suppressed during the incubation fast. To save
energy, triiodothyronine (T3) is adaptively decreased during fasting in most
bird species, despite T3 levels are maintained throughout incubation in female
eiders. However, the relationship between thyroid hormones and the immune
system is not fully understood. The current study aimed to determine the
endocrine mechanisms that underlie immunosuppression in incubating female
eiders. ...
