In order to stay warm during the harsh winter, birds and some animals have to embark on a long journey, during which they overcome hundreds and even thousands of miles away, heading in warm countries.
Migrating birds not only in the South but in the North of the country. For example, 2 species of thrushes from Scandinavia in the winter settle in the UK.
Naturally, birds overwinter where natural conditions are similar to conditions of life at home: forest - forested areas, coastal rivers, lakes and seas, Stepney in the steppes. Similarly, during the flight of the birds stick to the familiar and supportive seats. Forest birds fly over forest areas, steppe - on the steppes, and waterfowl move along river valleys, over lakes and sea coasts. Birds nesting on oceanic Islands, fly over the high seas. Cross the great sea of space and some continental birds. For example, gull-Kittiwake breeding off the coast of the Kola Peninsula, winter in the North-Western Atlantic and reach the West coast of Greenland.
Sometimes birds have to overcome during the flight unusual areas, such as deserts (in Central Asia - the Karakum desert in Africa, the Sahara and the Libyan desert). Birds trying to quickly pass such places and fly "broad front".
Autumn migration begins after the young learn to fly. Before flying birds often form flocks and sometimes wander long distances. Places with cold climates birds leave in the fall before the warmer region; in spring in the North they appear later than in the South. Each species of birds depart and arrive at a certain time, although, of course, the weather affects the timing of departure and arrival.
Birds of some species fly singly, others in groups or flocks. For many species characterized by a certain order of birds in the flock. Finches and other passerines fly disorderly groups, crow - rare chains, Curlews and sandpipers-magpies - line, geese and cranes - angle. In most birds the males and females fly at the same time. But the Finch females fly away in autumn before males, and storks males arrive in the spring home earlier than females. Young birds sometimes fly away for the winter before old. Some birds fly during the day, others at night, and stop to feed.
In some flocks of migrating birds every 10-15 minutes one of the birds observed in the middle of the jamb and flies, surrounded by her feathery relatives. After this time, its place is occupied by another bird, and so on. This is to ensure that each bird could rest. Indeed, in the centre of the pack it is not necessary to swing the wings: it carries the air flow.