The "assembly call" for migratory birds has been sounded again! How do they fly across mountains and seas?

Science Times reporter Ji Chunhong

The seasonal change of falling temperature and scarce food has once again sounded the rallying cry for migratory birds, opening the prelude to the global bird migration. Since the beginning of winter, tens of thousands of migratory birds have set out from all over the country, crossing mountains and seas in groups, heading south to find warm habitats, just like celebrating a "holiday".

This is a precisely planned migration journey. my country is an important channel for migratory birds. Four of the world's nine major migratory bird routes run through China, namely the East Asia-Australasia Flyway, the Central Asia Flyway, the West Asia-East Africa Flyway, and the Western Pacific Flyway, which almost cover all of my country's territory and territorial waters. During the long and complex flight, these little elves with super navigation capabilities can judge the time and determine their position and direction by the changes in the position of the sun, moon, and stars, as well as landmarks such as mountains, rivers, and coastlines. Not only that, they seem to have a "compass" hidden in their eyes, which can sense the earth's magnetic field to guide flight, and even use environmental clues such as polarized light, smell, and wind direction to assist navigation and keep the flight route from deviating.

Perhaps it is based on such a navigation system that they can accurately find the supply point during flight and reach the final destination. In Jiangxi, Poyang Lake, which is recuperating, has laid out a rich feast of fish and shrimp at the lowest water level to welcome nearly 600,000 migratory birds "home". On this important route for migratory birds from East Asia to Australasia, more than 95% of the world's white cranes, more than 80% of the Oriental white storks, and more than 70% of the white-naped cranes come here to spend the winter.

This is an arduous and long journey. In Dianchi Lake in Kunming, Yunnan, about 40,000 red-headed gulls flew here from Uvs Lake in Mongolia, the lake basin in Kyrgyzstan, the southern part of Lake Baikal in Russia, and the Bosten Lake basin in Xinjiang, my country. The shortest flight distance among them is nearly 4,000 kilometers, and the longest distance is more than 6,000 kilometers. Some of them need to fly over the Himalayas to reach their destination. In Sanmenxia City, Henan Province, tens of thousands of swans flying from Siberia have begun their new winter life in the Yellow River Bay.

This is a journey of self-improvement and transformation. Migration is the most difficult and most fatal "adventure" in the life of migratory birds. In this journey across mountains and seas, they will not only encounter strong air currents and turbulence in the air like humans flying on airplanes, but also experience unpredictable challenges such as storms, thick fog, and attacks by natural enemies, which affect their vision and cause them to lose their sense of direction or even lose their lives. In addition, the urbanization process of human society, changes in coastlines and topography will also affect migratory birds' judgment of familiar routes, just like people who have been away for many years and cannot find the way back to their hometown.

During the migration, the little migratory birds went through numerous hardships but still flew southwards...