Who migrates at night? 

In the UK, night migration is dominated by winter visitors. This includes wildfowl – geese, ducks, and other waterbirds, along with some smaller birds, often fieldfares and redwings. It’s these members of the thrush family that you’re most likely to hear, as they tend to fly at lower altitudes than wildfowl.

Why migrate at night? 

The nighttime atmosphere is often more constant and settled than in the daytime when thermals can result in turbulence. The calm nighttime air means birds can use less energy to fly long distances. It helps them maintain steady wingbeats and constant speeds. 

Avoiding predators is another reason for undertaking journeys at night. Most hawks and falcons hunt using their amazing eyesight to locate and chase prey. Migrating at night reduces this risk, especially for small birds which fly at comparatively slow speeds. 

In warmer parts of the world, birds also choose nighttime migration to take advantage of lower temperatures. It helps conserve water and energy supplies, while also avoiding overheating.

How to migrate at night 

The miracle of bird migration remains only partially understood. However, it seems that many birds use the stars to guide their direction of travel. 

These nighttime celestial cues are not necessarily the only navigational aids used by birds. An ability to sense the earth’s magnetic field, along with landmark recognition, also helps them determine their routes. Research also points to their ability to sense the smells of places over large distances, as well as ultra-low frequency sounds generated by, for example, the motions of the sea.

Bright city lights 

There’s growing evidence to suggest that light pollution from our buildings and streets is disrupting bird night migration patterns. Studies from North America have shown that birds can become disorientated by the high levels of artificial light pollution in cities, making it more difficult for them to orientate by the moon and stars. 

Here in the UK, bird charity British Trust for Ornithology (BTO) found that monitoring the flight calls of thrushes (one of the commonest nighttime migrants) revealed birds were five times more likely to be recorded crossing brightly lit cities than rural villages with little artificial light. This suggests that light pollution may disrupt flight patterns, attracting birds to deviate from their routes and wasting their valuable energy supplies on unnecessary detours.

You can do your bit for migrating birds (and other wildlife) by reducing light pollution at home.