Once you observe birds, you want to learn as much as you can about them. It is especially interesting to look into the mysteries of migratory birds that migrate seasonally. Every year birds travel enormous distances in a short period of time, sticking to fixed routes, and arrive at the same nesting and wintering grounds.
The great Greek scholar Aristotle (384-322 BC) wrote that birds fly away in the fall and return in the spring. He divided birds into those that live in the same places all year round and those that fly away or “disappear” for a while, like, say, pelicans, cranes or swallows. Aristotle explained the seasonal disappearance and appearance of some bird species by his own theory that some bird species turn into others. He also believed that many birds, such as storks, starlings, owls, thrushes, ducks, and skylarks, hibernate during the cold season.
For nearly two thousand years Aristotle’s views remained unshaken. As time went on, there was more and more reliable evidence of bird migrations. In an attempt to explain them, new, quite fantastic hypotheses emerged. For example, in the middle of the XVI century Swedish Archbishop Magnus suggested that swallows go to the bottom of reservoirs to winter. In two centuries an Englishman Johnson has supplemented this hypothesis with an original specification: swallows at first gather in a big flock, form a dense clump in the air and only then fall to the bottom of reservoirs.
Among the theories explaining the migrations of birds there were also space theories. According to one of them, it appeared that the birds winter not somewhere, but on the moon. Further it was explained that such a vast distance small and weak birds traveling on the backs of large, strong birds. And then where this “public transport” goes, the theory was silent.
Guiding marks
By the second half of the 19th century there was reliable evidence that European birds migrated to Africa and Southeast Asia for wintering. However, direct evidence only began to accumulate when ornithologists decided to tag birds before their seasonal journeys. Instead of the pre-existing most convenient tagging – a lightweight stainless zinc ring, on which the serial number, date and address are stamped – was invented and first used by a teacher from Denmark, Hans Mortensen, in the 1890s. Since then, the tagging of birds has been called ringing. One movement of the tongs and the ring is sent on a journey together with the feathery owner, so that after some time in another country or even on another continent it could be taken off the bird’s leg, the number and time could be recorded and sent to the indicated address.
Bird ringing has taken on a huge scale around the world. More than 50 million birds have been ringed in the United States and Canada alone, and each year about 600,000 birds are ringed in these countries. About the same number of birds are ringed in Europe. During Soviet times more than 300 thousand birds were ringed in Russia every year, nowadays the number is slightly less. Russia is a member of the International Committee on Bird Ringing and cooperates with national bird-ringing centers in 55 countries in America, Europe, Asia and Africa.
Ringers act very carefully and sometimes cleverly. To catch the birds they use almost invisible, thin nets which are hung in the places where the birds fly on long poles or tree branches. Thicker nets are placed on the ground and birds get entangled in them with their legs. There are even nets equipped with small “rockets”. When birds, nibbling on food scattered on the ground, come very close, “rockets” raise the net in the air, and it falls and covers the flock. And there are also nets that rise and close like a purse. Traps for birds are made in the form of a wide and long net funnel, ending with a receiving chamber. Food is poured into it as a bait. They also use such a method: at night they attract migrating birds with special lanterns and then cover them with a net.
In addition to ringing there are other methods of marking birds. For example, gulls with white plumage are marked with pink or red paint. This color does not come off for a long time; it is visible from a distance and does not disturb the bird’s life.
On average 3-5% of rings are returned to the ringing centers, but even this number is enough to get the exact information about where the birds fly to and by which routes they return home.
Who flies the furthest
Birds are very fast, extremely hardy, can fly several kilometers high, and are also highly oriented in the sky. There are real record-breakers among them.
The absolute champion on the distance of migration is the Arctic Tern – a white bird smaller than a gull with a black cap and a split tail, for which it is sometimes called a sea swallow.
Terns nest on the northern coast of the Arctic and on ice-free islands. Offspring appear in early June. And by the end of the short polar summer, the parental worries are over. The chicks are reared and fledged. It’s time to go to wintering. This is where the terns show what they can do.
Once on the coast of Labrador ringed fledgling can not yet fly, and 90 days later reared young tern caught on the southeastern coast of Africa, 14.5 thousand km from the nest. It is likely that this was not the end of the journey, as terns winter in the Antarctic seas. Another tern, which got a ring in our Arctic latitudes, found off the southern coast of Australia, it flew at least 22 thousand km. Some terns fly to their wintering grounds via the Pacific Ocean, while others choose the path along the western shores of Europe and Africa entering the Indian Ocean.
With the approach of spring, the terns head for the return journey and reappear in their native places, having in fact circled the globe. Some ornithologists said that our planet is not even big enough for such a flyer as a tern.
Other seabirds are also capable of traveling great distances. Take the wandering albatross. This large white bird with huge black wingspan up to 4 m at the ends spends much more time in the air than on water or land. The albatross uses air currents in flight, and this allows it to “glide” through the air without flapping its outstretched wings, which means it requires minimal effort. It picks up its prey from the water in flight. Neither hurricane wind, nor waves several meters high do not bother him, it’s as if the majestic bird does not notice any inclement weather. The migrating albatross can fly 15-20,000 km over the ocean and complete a “round-the-world” flight within a year.
The nesting period these fliers spend on small islands in the South Atlantic. In albatrosses it is unusually long – more than 11 months. When the chicks become “on the wing”, the parents’ wanderings continue. Albatrosses travel eastward along the 40th latitude of the Southern Hemisphere, nicknamed “roaring” because of incessant storms. At these latitudes, the albatross circles the Earth and in two or three years (for the next nesting) ends up on the same islands where it once hatched from an egg.
Another record-breaker in migrations is the sea petrel. Its home is on the small islets of the Bass Strait separating Australia and the island of Tasmania. Both parents strenuously feed the new chick, it quickly gains weight and fatness, and after a month and a half it weighs more than an adult bird. Feeding lasts for three months, then parents say goodbye to their offspring and fly away on their ways. Left without care, the chick starves for some time, and then begins to fly and fish little by little, and at last it flies away for the first time to a distant land, only to come back later.
First, the Slender-billed Petrels head for New Zealand, then turn north and, bypassing the islands of Oceania, end up off the coast of Japan. Then their route goes along our Far East coast to the Dezhnev Cape. Some birds fly over the Bering Strait and reach Wrangel Island. But the route doesn’t end there. From our shores they head for the Aleutian Islands, from where they turn southeast along the North American coast. After reaching California, the birds fly across the Pacific to the eastern shores of Australia. A little further south, and here are the home islands of Bass Strait and the old burrow, which has become dilapidated during the absence of its owner and requires repair. The annual route across the Pacific looks like a gigantic 20-25 thousand km loop. Apparently, we can consider the slender-billed petrel one of the most perfect flying creatures that ever lived on Earth.
The routes of birds of passage cover with a giant network all oceans occupying about 70% of the surface of our planet. But there are birds that fly primarily over land.
Across countries and continents
There are record-breakers among “land” flyers, too. One of them is called the puffin sandpiper. He got his nickname because the male, during mating games, puffs up his neck and lets out a muffled whistle. The Pectoral Sandpiper nests in the Arctic tundra of Canada, Alaska, and Siberia. His flight route – 14-15 thousand km – passes over the great plains of North America, through Mexico and Central America, and ends in the south of the South American continent.
There are other remarkable flyers in the sandpiper family. For example, the brown-winged plover, which nests in the Canadian tundra. After launching, plovers fly southeast and soon find themselves over the cold waters of the North Atlantic, near Labrador, Newfoundland, and Nova Scotia. Plovers are saved by their extraordinary endurance, for they cannot land on water. Plovers make a three-day dash across the ocean, overcoming in this time without landing almost 4 thousand km. However, some of the birds arrange a breather in the Bahamas and Antilles, but most of them do not stop in flight, reaching the green coast of Venezuela or Guyana.
Of record-breaking migratory flights over land, it is worth mentioning some species of swallows nesting in Northern and Central Europe and Scandinavia. They make their routes of 13 thousand km across all Europe and Africa.
The mute swan and whooper swan, nesting in remote places of Northern Europe and Asia, fly to the Mediterranean, Iran, Afghanistan, South and Southeast Asia for the winter, and in spring are among the first to appear in their native lands. Gray Cranes also keep up with them. These birds thoroughly prepare for the arduous flight, make test flights, work out the coherence and rhythm of movement, select flocks, train young birds. Rhythmically flapping their wide wings, the cranes fly in wedges. Some go to Africa and along the Nile reach Sudan; some cross Iran and stop at the shores of the Persian Gulf; some from Siberia reach India and Southwest China, but in all cases they fly 7-10 thousands km from home.
By September, white storks are on their way. Their routes, mostly crossed by gliding flight, lie over land. Storks cross water bodies only when the opposite shore is visible.
If storks nest in Europe west of the Elbe, the flock flies to Gibraltar. To force the narrowest, 16-kilometer portion of the Strait of Gibraltar, the birds gain high altitude over Spain and begin to glide toward Africa, taking advantage of air currents and rising heat currents. Some of the birds remain in the west of the continent, while others traverse the world’s largest desert, the Sahara. Then, deviating to the southeast and then to the south, storks cross the equatorial forest belt. After flying about three-quarters of the African continent, they finish in South Africa, leaving behind 12,000 to 13,000 km.
If storks nest east of Elba, the flocks head for the Bosporus, round the Mediterranean Sea from the east, fly over Palestine, Egypt, along the Nile valley, and arrive in South Africa, having covered the same 12,000-13,000 km.
It’s worth mentioning the birds that set records for the height of flight. These are, undoubtedly, greylag geese seen at altitudes of 8850 and even 9100 m above the highest mountains of the planet, the Himalayas. At such altitudes, even trained climbers need oxygen, and acclimatization is necessary before climbing. This does not apply to geese. During the flight they can be content with small amount of oxygen for at least one and a half to two days and they do not lose their ability to work.
This incredible flight through the Himalayas looks something like this. In the fall, flocks of gray geese gather in southern Siberia, resting and feeding before migrating. One day at dawn, they take off, gain maximum altitude, and head toward the giant mountains shining with glaciers and snowy peaks. At the head of the flock, walking in a wedge, flies an experienced leader, who knows all the saddles and passages between the mountains. The birds spend many hours in the 40-degree frost. Finally, the peaks of “eight-thousanders” are left behind. Two or three hours of flight more, and below there are the hills and forests of Northern India. The leader chooses a place to rest, and the death-weary birds descend to a small island in the middle of a secluded lake.
Only geese, and perhaps some grouse, are capable of such height records. Most birds keep their flights at heights of about 1500 m. On clear nights they can rise even up to 6 thousand meters.
According to some scientists, about 30% of birds which have flown away for winter come back to their nesting places. The rest die due to sudden changes in weather, storms, winds, frosts, lack of strength and other difficulties. But every year in the fall, instinct lifts millions of birds from their nest, and they fly off on their own, often incredibly long routes to survive the winter, return again and produce offspring that will replicate exactly the path of their parents.
No responses yet