Many animals migrate in large groups towards their wintering grounds. However, what is the significance of travelling in swarms, herds, or flocks? Our research group studies the effects of the social environment on the movement decisions of migrating birds. We are interested in understanding how social behavior affects migration by studying these impacts at different levels. For example, how do members of the same group interact with each other at submeter scale? Are there individual differences between group members, and how do they influence leadership or movement decisions? Additionally, we are also monitoring global, long-term effects at the individual and group-level by examining how sociality influences the ontogeny of migratory patterns, movement costs, and overall fitness. To answer these questions, we use a combination of high-resolution multi-sensor tracking and behavioural experiments.