The majority of migratory birds fly at night. Species that commonly make this journey in the dark include sparrows, warblers, orioles, thrushes, and ducks, just to name a few examples. Evolving to migrate at night is beneficial to the survival of birds in many ways.
Nocturnal migrants use the stars and moon for navigation
Studies show that some species use a star compass to navigate, meaning they learn north-south orientation from a rotational star pattern.
Nocturnal migrants can more easily avoid predators
Daytime predators, such as hawks and falcons, pose a threat to migrating species that may be less acrobatic flyers. Flying at night allows these birds to take advantage of a time when many common predators are inactive.
Nocturnal migrants take advantage of calmer air
Nighttime migration helps birds avoid daytime thermals that usually make for rougher flights. Smoother flights mean less energy spent during migration.
Nocturnal migrants are less likely to overheat
Migration is a behavior that produces a lot of heat from exerted energy. The cooler air at night allows birds to maintain a lower internal temperature during their journey.
Night Migration Under Threat
Many cities as well as traditionally remote areas have seen significant population growth, and light pollution is growing exponentially in those areas. Studies show that artificial light at night (ALAN) is often greatest along major migration routes. ALAN causes disorientation, leaving migratory birds susceptible to exhaustion, predation, and collisions.