One of the most amazing and fascinating facts about birds is their ability to travel thousands of kilometres each year so that they can spend the winter in a warm and pleasant climate. It is extraordinary how they gather together to fly away every year.
Most birds migrate to look for food - in the winter in Europe it is not easy to find the food that they find in the summer, such as insects, fruit and seeds. But there is plenty of such food available in other parts of the world. Migration makes it easier for such birds to survive, although some may die during the journey.
To be able to survive migration, birds must be healthy with a bulid up of fat and fresh feathers. When the breeding season is over and before they migrate, birds go through a 'complete refurbishment'. They accumulate fat reserves under their skin. The old and worn summer flight feathers fall out and new ones appear in their place.
Birds get much of the information they need from their surroundings while they migrate. There are three basic sources of information for them - the sun, stars and the earth's magnetic field. Birds observe the location of the stars and sun as they fly, and they can feel the magnetic field with a special receptor placed just over the beak.