2025/07/01 by Erica Calabretta, Virginie Canoine, Massimiliano Cardinale +2 · 1 voice
Environmental Science · Agricultural and Biological Sciences · Earth and Planetary Sciences · #Climate variability and models #Animal Behavior and Reproduction #Cryospheric studies and observations
paper · pdf · doi:10.1002/jav.03474
Migration is an energy‐intensive phase of birds' life cycle, often including the crossing of large ecological barriers during non‐stop flights. Corticosterone (CORT), an adrenocortical hormone also known as the stress hormone, generally rises at the onset of migration to facilitate and sustain high‐energy metabolism. Although birds can select favourable meteorological conditions at departure, weather variability en route may affect the migrants' energy reserves and their ability to cope with other stressors. This study investigated the effects of weather conditions on the physiological status of two nocturnal trans‐Saharan species, the common whitethroat Curruca communis and the garden warbler Sylvia borin , upon arrival at a stopover island after crossing the Mediterranean Sea during pre‐breeding migration. We assessed fuel stores and CORT variations in relation to tailwinds and air temperature experienced over the sea route. Birds that arrived at the stopover site with residual energy reserves after encountering moderate headwinds or lower temperatures had similar baseline CORT concentrations compared to those that migrated with tailwinds and higher temperatures. While both species exhibited a normal stress response to catching and handling, stress‐induced CORT levels were correlated with higher temperature only in garden warblers. Our study provides novel insights into CORT dynamics, suggesting that nocturnal migratory Passerines are not largely affected by weather variability across a marine barrier during pre‐breeding migration if they have sufficient energy reserves.