Cost of reproduction in a long-lived bird: incubation effort reduces immune function and future reproduction.
Life-history theory predicts that increased current reproductive effort should lead to a fitness cost. This cost of reproduction may be observed as reduced survival or future reproduction, and may be caused by temporal suppression of immune function in stressed or hard-working individuals. In birds, consideration of the costs of incubating eggs has largely been neglected in favour of the costs of brood rearing. We manipulated incubation demand in two breeding seasons (2000 and 2001) in female common eiders (Somateria mollissima) by creating clutches of three and six eggs (natural range 3-6 eggs). The common eider is a long-lived sea-duck where females do not eat during the incubation period. Mass loss increased and immune function (lymphocyte levels and specific antibody response to the non-pathogenic antigens diphtheria and tetanus toxoid) was reduced in females incubating large clutches. The increased incubation effort among females assigned to large incubation demand did not lead to adverse effects on current reproduction or return rate in the next breeding season. However, large incubation demand resulted in long-term fitness costs through reduced fecundity the year after manipulation. Our data show that in eiders, a long-lived species, the cost of high incubation demand is paid in the currency of reduced future fecundity, possibly mediated by reduced immune function.
Hanssen
Sveinn Are
SA
Department of Animal Ecology, Lund University, Ecology Building, 223 62 Lund, Sweden. sveinn.a.hanssen@nina.no
Hasselquist
Dennis
D
Folstad
Ivar
I
Erikstad
Kjell Einar
KE
D000704:Analysis of Variance; D000818:Animals; D046090:Anseriformes / Q000276:immunology* / Q000502:physiology*; D000917:Antibody Formation / Q000276:immunology*; D001835:Body Weight; D004168:Diphtheria Toxoid / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005298:Fertility / Q000502:physiology*; D006386:Hemagglutination Tests; D008214:Lymphocytes / Q000097:blood; D009425:Nesting Behavior / Q000502:physiology*; D009664:Norway; D012098:Reproduction / Q000502:physiology*; D013745:Tetanus Toxoid / Q000276:immunology
D004168:Diphtheria Toxoid; D013745:Tetanus Toxoid