Autumn is the time when migratory birds set off on a long and difficult journey, overcoming thousands of kilometers from the places where they were born. Here are some interesting facts about such travel.
Many birds, such as cranes and geese, fly in flocks in a V-shaped wedge. Why is it so? The fact is that a bird flying in front creates an air flow, which makes it easier for those who follow it. Accordingly, the greatest load falls on the leader of the pack flying in front. The angle of this wedge is 55 degrees.
How do birds navigate along the way? It must be admitted that there is no exact answer to this question yet. It was believed that the younger generation learns the route when they fly with more experienced birds. The assumption turned out to be wrong. Experiments were carried out when young birds were taken away hundreds of kilometers from their native nests, and when they were released, they flew unmistakably to the place of wintering of other relatives. There is an assumption that birds sense the magnetic field of the earth, therefore, they do not go astray even in conditions of limited visibility.
The length of the daytime flight is not the same for birds of different species. Ducks are able to overcome 150-200 kilometers, but woodcocks - up to 500. The speed of birds also differs. For example, quails fly at a speed of about 40 km / h, but black swifts - about 150.
Climbers claim to have seen flocks of geese flying over the Himalayas at over 8, 000 meters above sea level. At the same time, there is 30% less oxygen than on the plain.
Arctic tern migrates annually from the Arctic to the Antarctic, the total length of the annual route is about 70, 000 kilometers. And if we take into account that the average life span of a tern is 20-25 years, then during this time it could fly three times from the Earth to the Moon and back.
In 1974, swallows from Europe were sent south by train and airplane. The fact is that already at the beginning of September, unusually cold and rainy weather set in Germany and Switzerland. In such conditions, the search for insects was difficult and many birds died of hunger. Volunteers raised funds to send swallows to the Mediterranean.
Interestingly, in the ancient world, the seabed was considered the wintering place for swallows. This belief appeared due to the fact that swallows often fell into the nets of fishermen. In fact, the weak individuals simply did not have enough strength to fly, and they died in the depths of the sea.
Why do birds cover such distances twice a year? The main reason is a significant reduction or complete absence of the food supply in winter. Those species that are able to forage in winter are sedentary. They do not leave their permanent habitats.
By the way, the threat of hunger makes birds migrate north in the spring. In wintering places, such a number of birds accumulate that it will no longer be possible to feed the chicks and most of them will die. The instinct of procreation attracts birds to where in the summer conditions are quite favorable and there is an opportunity to feed their offspring.