A new doctoral thesis by Cassandra Ugland from Norway's NTNU (Norwegian University of Science and Technology) Department of Biology investigates how the first winter experiences of European shags—also known as Phalacrocorax aristotelis—might influence their migration patterns. The study, published in the Journal of Animal Ecology, explores the factors that determine whether these birds migrate to find food during the winter or stay in their breeding areas. As climate change continues to alter seasonal patterns, it may prompt animals to adopt new survival strategies, including changes in migration behavior. European shags breed on the Isle of May, a small island off the east coast of Scotland. In this population, roughly half of the birds remain in the same area during the winter, while the other half may travel north along the coast. Ugland’s research examined how factors such as natural selection, genetic differences, and the ability to adapt behaviorally influence whether a young bird migrates or stays put during its first winter. To do this, she analyzed data from bird-banding programs and used advanced statistical models to look at how variation, selection, and genetics affect the birds' early-life decisions. The study found that there is significant variation in migration behavior among individual birds and from year to year. However, it also revealed that the choices birds make during their first winter are especially important in shaping their future behavior. While other factors like genetics and the environment also play a role, the early experiences of each bird seem to have a major influence on whether it migrates or remains in its breeding area. This suggests that the environment a young bird encounters during its first winter could shape its long-term behavior, including its migration patterns. The research also highlights the complex interaction between environmental conditions, the ability of birds to learn and adapt through experience, and the pressures of natural selection over time. These factors together determine the extent of migration within the population. While the study provides important insights, more research is needed to identify which specific environmental factors are most influential in shaping these behaviors. Understanding these dynamics can help scientists better predict how wildlife will respond to ongoing climate change.