Swallows are a very common bird that is small and flexible in their bodies, with black and white plumage, forked tails, and short, wide beaks, which are suitable for catching insects in the air. The swallow is a migratory bird that migrates every year from north to south or from south to north. The migration of swallows often occurs overnight, making for surprise and curiosity. Why do swallows migrate, how do they migrate, and where do they winter? Let's explore these questions.
Why do swallows migrate?
The migration of swallows is an adaptation to changes in the environment. The main food of swallows is insects, and the activity of insects is affected by the temperature. When temperatures drop in the north and insects decrease or hibernate, swallows fly south in search of more food. When temperatures rise in the south and insects increase or breed, swallows fly back to the north to avoid excessive competition and predation. Therefore, the swallows migrate not because of the cold, but because of the amount of food.
The migration of swallows is also a breeding strategy. Swallows generally breed in the north, where summer has longer days, more food, and is more suitable for raising young birds. Swallows build nests on human houses or structures such as bridges, and are made of a mixture of earth and saliva in the shape of half a bowl to protect their eggs and young birds from outside interference. Swallows generally lay two to three nests of eggs per year, four to six per nest, with an incubation period of about two weeks and a brooding period of about three weeks. When the young birds are old enough to fly and forage on their own, the swallows take them with them to the south in search of warmer places to spend the winter.
How do swallows migrate?
The migration of swallows is an amazing flight. Swallows can fly at speeds of up to 40 kilometers per hour and migrate over distances of thousands of kilometers or even tens of thousands of kilometers. Swallows have a very complete navigation system, they can use the sun, stars, geomagnetism, terrain and other clues to determine their own direction and position. Swallows also have a very strong memory, they can remember their birthplace and wintering place, as well as food and water sources along the way, and migrate along the same or similar route every year.
The migration of swallows is also a kind of teamwork. Swallows usually do not migrate alone, but in flocks, forming a "V" shaped queue. The advantage of this is that it can reduce the resistance of the air, save energy, and also exchange information with each other, improving safety. During their migration, swallows encounter various difficulties and dangers, such as storms, thunder and lightning, predators, human interference, etc., and they need to support and encourage each other in order to reach their destinations smoothly.
Where do swallows winter?
The wintering grounds of swallows are a variety of options. The wintering grounds of swallows depend on their birthplace and migration route. Different species of swallows have different wintering grounds. In general, swallows choose warm, moist, and food-rich places for wintering, such as South Asia, Southeast Asia, Africa, etc. Some swallows will overwinter in the south of China, such as Guangdong, Guangxi, Yunnan, Fujian, etc., and some swallows will even overwinter in the north of China, such as Beijing, Hebei, etc., these swallows are usually rock swallows, they can find enough food and habitat in the winter in the north.
The wintering grounds of swallows are also a flexible variation. The wintering grounds of swallows are not fixed, but will be adjusted according to the change of the environment. For example, if the climate warms up and insects increase in a certain place, swallows will choose to overwinter there instead of continuing south. If the climate in a certain place gets colder and the insects decrease, the swallows will leave there in search of a more suitable place. The wintering grounds of swallows are also affected by humans, for example, if human buildings, agriculture, pollution, etc. pose a threat to the survival of swallows, swallows will avoid those places and choose safer places.
The migration and wintering of swallows is a miracle of life
The migration and wintering of swallows is a miracle of life. They demonstrate the wisdom, courage, tenacity, and resilience of life. They also bring beauty, joy, and inspiration to humanity. Swallows are a bird that has a deep affection for humans, they are friends and teachers of humans. We should respect and protect swallows so that they can fly freely and enjoy the journey of life.
In the process of migrating and wintering, swallows undergo some magical changes
In the process of migrating and wintering, swallows not only have to face the challenges of various environments, but also adjust their bodies and behaviors to adapt to different conditions. During the migration and wintering process, swallows undergo some magical changes, such as:
Change in weight
Before migrating, swallows eat large quantities to gain their weight and fat to store enough energy. The weight of the swallow can be increased to two or even three times the normal weight. In this way, the swallows can burn their own fat and maintain their body temperature and metabolism during long-distance flights. During their migration, swallows are constantly losing their weight, sometimes even to less than half of their normal weight. In this way, the swallow can reduce its flight resistance and improve its flight efficiency. After migration, swallows return to their normal weight to adapt to their new environment and food.
Changes in body temperature
During their migration and wintering, swallows encounter a variety of different temperatures, sometimes as high as 40°C and sometimes as low as -40°C. Swallows have a special ability to regulate their body temperature and adapt it to the ambient temperature. The normal body temperature of a swallow is 41°C, but during migration and wintering, swallows can lower their body temperature even below 10°C. In this way, the swallows can reduce their energy consumption and prolong their survival time. When the swallow lowers its body temperature, it enters a state similar to hibernation, called "deep sleep", in which the swallow's heart rate and breathing are greatly reduced, and there is almost no activity. When the swallow recovers its body temperature, it will shake its wings to increase its blood circulation and reactivate its body functions.
Changes in heart rate
During migration and wintering, swallows regulate their heart rate according to their flight status and body temperature. The normal heart rate of a swallow is 400 beats per minute, but during migration and wintering, the heart rate of a swallow can vary greatly, sometimes as high as 1000 beats per minute, sometimes as low as 10 beats per minute. When flying, swallows raise their heart rate to increase their oxygen supply and support their muscle activity. When the swallow is resting, it lowers its heart rate to reduce its energy expenditure and protect its organs. When the swallow is in a deep sleep, it will lower its heart rate to the lowest level to achieve a state close to death, so that the swallow can maintain its life in extreme environments.
Metabolic changes
During migration and wintering, swallows regulate their metabolism according to their food sources and energy needs. The normal metabolism of swallows is to consume 0.5 grams of fat per hour, but during migration and wintering, the metabolism of swallows can vary greatly, sometimes up to 2 grams of fat per hour, sometimes as low as 0.1 grams of fat per hour. When swallows fly, they increase their metabolism to use their fat and generate enough heat and power. When the swallow is resting, it will lower its metabolism to save its fat and prolong its flight time. When swallows are in a deep sleep, they will lower their metabolism to the lowest level to reduce their heat loss and maintain their body temperature.
The migration and wintering of swallows is a kind of wisdom of life. They use their bodies and behaviors to adapt to different environments and conditions. They also bring beauty, joy, and inspiration to humanity. Swallows are a bird that has a deep affection for humans, they are friends and teachers of humans. We should respect and protect swallows so that they can fly freely and enjoy the journey of life.