Within seasons and among years: When are corticosterone levels repeatable?

► Are corticosterone (CORT) concentrations in two wild bird species repeatable? ► Baseline CORT was repeatable over short time spans during the breeding season. ► Baseline CORT was not repeatable over longer time intervals. ► Stress-induced concentrations of CORT were not repeatable. ► Corticosterone concentrations are plastic traits.