Every spring and autumn, birds fly in groups in the sky, covering the sun. This seasonal phenomenon of changing habitats in different seasons, or moving from nesting sites to wintering sites, or returning from wintering sites to nesting sites is called bird migration.
Every spring, birds begin a series of activities, such as courtship, reproduction, nesting, hatching and brooding. Birds rarely get lost in flight, no matter how long the journey is.
Extended data:
distribution range
Birds are found in most land habitats. Birds are distributed on seven continents, and even snow swallows can be found in the Antarctic inland 440 kilometers away from the ocean.
The diversity of birds is most remarkable in the tropics. In the early days, people thought that the high diversity in the tropics was the result of high speciation, but recent research found that high speciation also occurred in high latitudes, but it was offset by the higher extinction rate in the tropics.
Many birds can live on land and in the sea. Some seabirds go ashore just to breed, and some penguins can dive to a depth of 300 meters.