The amazing "footless bird" almost never touches the ground in its entire life. It sleeps and mates in the air.

Have you ever heard of a bird that spends almost its entire life in the air? Except for reproducing offspring, it hardly needs to land, and can even sleep and mate in flight. This bird is the swift, which is called the "footless bird" because its feet have degenerated to such a small size that it cannot walk or jump on the ground. The swift is the most capable bird in flight. It can fly continuously for ten months without landing. Every year, it migrates from the Eurasian continent to Africa for wintering, and then returns from Africa to the Eurasian continent to reproduce. The swift's flying speed, endurance and adaptability are amazing. It is a true "pilot".

1. The special body structure of swifts

Swifts belong to the family Apodidae of the order Apodidae. There are nearly 100 different species distributed all over the world. The most common of these is the common swift (Apus apus), which is also the subject of this article. The common swift is about 16 cm long and weighs about 40 grams. Its feathers are black or dark gray, and its beak and eyes are large. The most notable feature of the swift is its wings, which are long, narrow, and sickle-shaped, allowing the swift to flexibly turn and accelerate in the air. The swift can reach a speed of 110 km/h in level flight, which is faster than many predators. Another feature of the swift is its feet, which are very small and all four toes are facing forward (one of the toes can rotate freely), which allows the swift to cling to vertical surfaces such as tree trunks, cliffs or buildings. However, this also means that the swift cannot stand or walk on flat ground, and if it accidentally lands, it is difficult to take off again. Therefore, swifts try to avoid landing on the ground, hence the name "footless bird".

2. The amazing flying ability of swifts

Swifts are migratory birds that need to fly from Eurasia to Africa for wintering and then fly back from Africa to Eurasia for breeding. This means they need to fly nearly 30,000 kilometers each way. Moreover, during this long journey, swifts almost never stop flying. Except for about two months of incubation and raising chicks in the nest, swifts remain in flight for 99% of the time. Scientists have installed micro data recorders and accelerometers on some swifts to track their flight routes and activities. It was found that some swifts flew for ten whole months without landing once. This may not be the limit, because some swifts may not land within two years after learning to fly until they are sexually mature and begin to reproduce. This means that swifts can fly back and forth between the earth and the moon several times in their lifetime.

3. The aerial lifestyle of swifts

Since swifts rarely land, how do they live in the air? First of all, swifts are insectivorous birds, and they mainly feed on flying insects. Swifts have large mouths that can be opened to catch various flying insects in flight. Swifts also skim the water surface and drink a few sips of water. Secondly, swifts are social birds, and they usually fly and forage in groups. In the air, swifts also engage in courtship and mating behaviors. Male swifts will use calls and flying postures to attract the attention of female swifts. If they get a response, the two swifts will hug each other tightly in the air to complete the mating process. Finally, swifts can also sleep in the air. Scientists have found that swifts can use a method called unihemispheric slow-wave sleep (USWS) to rest. This method refers to letting only one side of the brain enter a deep sleep state, while the other side of the brain remains awake. In this way, swifts can relax and recover their bodies to a certain extent while maintaining flight balance and being alert to external dangers.

4. Current situation of swifts

Swifts are very magical and lovely birds, and they have important ecological value and cultural significance to humans. For example, in traditional Chinese culture, swifts are regarded as symbols of auspiciousness and loyalty, and in European culture, swifts are considered messengers of spring and happiness. However, due to factors such as urbanization, climate change, and human interference, the living environment and resources of swifts are seriously threatened. Many places suitable for swifts to build nests and forage for food have been occupied or transformed by humans, resulting in the loss of swifts' habitats. At the same time, due to the use of agricultural chemicals and air pollution, the number of flying insects in the air has also been greatly reduced, making it difficult for swifts to find sufficient food. Therefore, the number of swifts is showing a downward trend worldwide.