Although the icy darkness of an arctic winter may seem daunting, lack of food is the biggest problem for birds during the cold season: terrestrial insects are killed by frost, plants and seeds lie covered in snow, and both marine and fresh waters are sealed over with ice. Most arctic birds resolve this difficulty by heading south for the winter and 85% of them migrate to areas where more food is available – from southern Canada to the sunny coasts of Mexico, or even the farthest tip of South America!

In some species, males begin to store up energy for migration as soon as they have finished breeding, getting out early and leaving the females to raise the chicks. This is because as the short summer progresses, resources become fewer and competition grows more fierce. As soon as their offspring are able to look after themselves, the females follow the males, leaving the juveniles behind to fend for themselves. As soon as the young birds can fly well enough to migrate successfully, they too leave the Arctic – a remarkable journey, given that they have no adults to show them the way!

Even birds that normally winter in the Arctic sometimes move south in search of food. For example, in years when lemmings are scarce in the Arctic, snowy owls travel to southern Canada where more prey are available.