The northern wheatear (Oenanthe oenanthe) makes one of the world's longest migrations for a small bird, travelling from Alaska and Greenland to sub-Saharan Africa each year.
Migration imposes extreme physiological stress, including organ remodelling (digestive tract shrinks to fuel flight) and sleep deprivation during Zugunruhe. Stopover site quality critically determines migration success — birds arriving at degraded stopover habitats face starvation and exhaustion. Light pollution disrupts migratory orientation, increasing collision mortality. Conservation of upland breeding habitats supports population welfare.