In ethology, zugunruhe is anxious behavior in migratory animals that are prevented from migrating, especially in birds. When these animals are enclosed, they exhibit this behaviour during the seasons in which they normally migrate. Behaviourists have been able to study the endocrine controls and navigational mechanisms associated with migration from studying zugunruhe.
This term is German in origin and is a compound of Zug (move, migration) and Unruhe (anxiety, restlessness).
Adrenocortical hormones are known to act in concert with prolactin in stimulating this behavior in White-crowned Sparrows.
Mohinder: When a change comes, some species feel the urge to migrate. They call it zugunruhe. A pull of the soul to a far-off place. Following a scent in the wind, a star in the sky. The ancient message comes, calling the kindred to take flight and gather together. Only then can they hope to survive the cruel season to come.