Do you know where the swallows will spend the winter? It is said that swallows migrate to the north to nest in the spring and leave in the winter for the warm south. But in fact, in the southern region of our country, people have basically never seen swallows when cooling down.
In order to study this problem, in 2014, a professional scientific research team installed a positioning device on the body of a Beijing Swift, hoping to determine where the "south" of the swallow is through real-time positioning. The Beijing Swift left Beijing in July, but instead of flying to a coastal city southeast of China, it flew toward Hebei, then through Xinjiang, over Iran, and finally settled in southern Africa, 25,000 kilometers from Beijing.
This result once made the team wonder if they had caught the swallows wrong, but after a lot of comparative experiments, they determined that swifts would really fly to Asia in the spring and actively fly to Africa in July. Most of the other species of swallows will fly to parts of Africa after cooling down.
So why didn't the swallow settle down in China's warm southern coastal city, but instead chose to travel thousands of miles to Africa? Is Africa really that good?
If you want to know the answer to this question, you must first understand the climate difference between our country and Africa. China's north is deep inland, most of the region is affected by the temperate continental climate, spring and summer precipitation is scarce, the temperature is high, autumn and winter precipitation is relatively rich, the temperature will be relatively low.
However, China's southern cities are mainly affected by the monsoon climate, the winter climate is relatively warm, and the precipitation is maintained at more than 1000 mm all year round. And regardless of the north and south of our country, autumn and winter are very prone to windy weather. This has a great adverse impact on the migration process of swallows.
The swallow belongs to the order Finches, which are small in size, with pointed and narrow wings, thin claws, not too many feathers, and no strength. Although it is one of the most flexible finches, this flexibility also causes them to be too thin. It should be known that an adult swallow weighs only about 50 grams, and if there is a stormy weather on the way to migration, the process of swallow migration is most likely interrupted.
So what about Africa? Completely different from China, Africa spans the equator from north to south, and has been exposed to direct sunlight for a long time, resulting in a more simple local climate composition and very high temperature, so Africa is also known as a "tropical continent". There are only rainy and dry seasons, and the whole year is hot and rainy, dry and hot.
Although temperatures in Africa will be centered on the equator, they will gradually decrease along the north-south direction. However, the average annual temperature of the continent above 20 °C still accounts for more than 95% of the continent's area.
And this extreme weather makes the precipitation in Africa appear to be very uneven. With the exception of some sea-based areas that receive small-scale precipitation during the rainy season, most of the rest of Africa is almost in a year-round rain-free state, with an average annual precipitation of less than 200 mm in 1/3 of the continent.
At this time, let's look at the migration route of the swallows: from Hebei, to Xinjiang, into Iran, to Africa... Almost every region of the route happens to be in the rainy or dry season, and the chance of encountering storms on the way is minimized. Therefore, taking such a route can ensure the safety of migration to the greatest extent.
Of course. The swallows did not choose to travel to Africa for safety reasons, but more importantly, there was more food on the African route. Swallows are not camels, and during the migration, they must first ensure that there are stable "three meals" to complete the energy replenishment. And even if it is a camel, it is estimated that it will have to eat a lot of food after walking more than 25,000 kilometers in 2 months.
The areas through which the African route passes, temperatures are still rising. Insects are numerous and tenacious, and there are often large numbers of insects flying together to plague crops.
Coincidentally, swallows also happen to be one of the best birds to fly. It is also an expert in insect catching. Especially during migration, in order to ensure progress, they can even prey on the course of flight. In this way, the farmer saves the crops and the swallows replenish the energy, which can be said to be the best of both worlds.
Not only that, but most of the swallows stop flying except when they are sleeping, drinking water and nesting and brooding, and they are in flight at other times. The swift can even sleep in the air, and if it flies non-stop in one direction, it can fly more than 1200 kilometers a day.
Such a speed can almost complete the 25,000 kilometers of migration in 2 months, and when the swallows fly to the South African region, they can rest here. Until February of the following year, after the swallows had eaten and drunk enough in South Africa, they "returned to China in situ". But if swifts choose to live in southern China, they will soon encounter a severe "famine."
As long as you are familiar with farming, you know that in the autumn and winter of our country, the climate is cold, most of the adult insects have been frozen to death at this time, and the larvae are still lurking in the ground in the form of insect eggs or attached to the seedlings of the plant, which is not conducive to swift predation. If you want to stay in our country all the time, it is estimated that you can only learn squirrels to dig a warm tree hole, where you can store grain for the winter.
Then some people will surely ask, if Swift wants to go to Africa, why not fly directly over, but instead take a long detour? The straight-line distance between Beijing and South Africa is only 12,000 kilometers, and from the map, the straight line is indeed closer. But don't forget that there is an Indian Ocean and an Atlantic Ocean spaced between the two places, and although the swift itself is fast enough, it is completely unstable enough to cross the ocean directly.
Moreover, circumventing from Xinjiang can avoid a large area of plateau mountain range in China. If swifts fly southwest from Beijing, although it will reduce the distance, it will definitely pass through the Qinghai-Tibet Plateau and the Himalayas on the way, where the low temperature is not suitable for birds, and the towering mountains will block the migration process of swallows. And there won't be any food along the way, so it's not good for Swifts to fly for long periods of time.