Leukocyte coping capacity as a complementary stress metric in migrating birds

Corticosterone (Cort) is involved in multiple physiological processes during bird migration, complicating its interpretation in a stress context. We investigated whether the leukocyte coping capacity (LCC) provides useful complementary information on the stress response in migratory Garden Warblers (Sylvia borin) and how it relates to Cort and energetic condition. Contrary to Cort levels, LCC significantly decreased, implying high-stress levels and a diminished capacity to recover after a stressful event. The absence of significant effects of body conditions on the stress parameters shows no simple relationship between these traits and highlights the need for additional stress metrics to measure stress in life-history contexts.