The natural world is wonderful. The most well known form movements of birds – migration. This method of changing habitat area is characterized by a fairly high speed and is not accompanied by a long occupation of the site. Often, migration repeated periodically over some small time, and in such cases we speak of periodic movements. When the migratory range is placed at 12 months, these displacements are seasonal, such as: fall and spring flights of birds, the annual migration of elk, deer, deer, moving from areas with more snow in snowy regions, the migration of antelope (including the Russian Saiga in Kazakhstan and the Caspian Sea) because of the drought; movement of seals, fur seals, whales, and various other animals and fish migrations are. Pronouncing 'seek fresh water', 'looking for land', 'fleeing from the cold', we mean not fundamentally different methods of movement (as it may seem at first), but in general the same – repetitive movements. This phenomenon has the character every time the mass movement, though not always well marked.
Residents are accustomed to always see the ordinary, gray crows. But does not everyone know that crows liking from December to March, flocks of garbage and spending the night in Moscow's avenues, were born far from the suburbs, in the northern forests, and only come here to winter. There will come a month of spring, and the ravens gradually give way to returning to the warm countries, and not differing from the outside the brothers will fly to nest in their home in Volgograd and the Murmansk region. Base, causing the annual migration, usually complex. Topics at least the most palpable among them all the same just hunger, but not cold.
There are events where migratory birds stay to winter in the field of severe frosts. The main thing – a very large tracts of land not covered with snow and not zamerzschie ice of the river, where possible turn up sufficient food. We must not forget that during winter daylight is short, and if during these hours do not eat for a long night, the heat transfer and disrupted frost will do the trick. That is why under the trees, where to spend the night frosts crows, very often you can find them frozen and crouched bodies. And for this reason, so no fun, carefree diving ducks, the typical migratory birds in the water among the ice pans in the zoo! And sometimes Other reasons forcing the animals to leave their areas and migrate to others. For example, the May passage of deer grazing on the high caused by insects: mosquitoes, gadflies, gadflies. Animals in the summer will not stop shaking their heads, snort, running from place to place. And just going out on some hill, relax and calm down. What's the matter? And just started a breeze, and the little tormentors disappeared. And herds of animals plodded toward the Arctic Ocean. Our source: The ethnographic literature