Testosterone and avian life histories: The effect of experimentally elevated testosterone on corticosterone and body mass in dark-eyed juncos

摘要: Abstract To assess whether alterations in the normal pattern of testosterone (T) secretion might be beneficial or detrimental, we studied a breeding population darkeyed juncos which elevated T experimentally and measured its effect on potential correlates fitness. We treated both free-living captive males with implants that were either empty (C-males, controls) packed (T-males, experimentals). Timing implant varied was designed to mimic natural peak levels except peaks prolonged premature. bled birds at recapture analyzed their plasma, female mates, for corticosterone (B). also body mass fat score T- C-males. In field, T-implants kept it least month. Experimental had higher B than controls. captives, plasma detectable within 24 hr. T-males again females, neither nor differed between mates implanted early spring lost more late did controls lower scores when recaptured. When inserted summer, treatment not influence mass. Elevated apparently hastened transition from winter mode storage. suggest elevation selected against because association B. Premature costly resultant loss reserves, could lead mortality snowstorms prevent access food.