Genomic Integrity in Gull Chicks Predicts Colony Departure and Postfledging Movements.

In species with parental care, the transition from dependence to independence is a critical stage during which juveniles must make key decisions for their future life. In colonial birds, the physiological state of juveniles during this transition may influence the timing of colony departure and subsequent movement patterns. Telomere length and DNA damage have been proposed as important biomarkers of early-life stress and physiological condition, which can predict an individual's capacity to cope with environmental challenges during the postfledging life. Here, we analyzed telomere length and DNA damage in blood samples of fully grown yellow-legged gull chicks and monitored their postfledging movements using GPS tracking. All individuals left their natal colony between 52 and 84 days of age. Those with shorter telomeres and higher levels of DNA damage left the colony earlier, possibly due to reduced parental provisioning and poor competitive ability for resources. Females and those with higher DNA damage settled farther from the natal colony. These findings suggest that physiological state at the end of the developmental period influences key decisions during the transition to independence, with potential consequences for population dynamics.