Every year, they need to fly continuously for about 7 hours, and they will stop to have a rest at night. This is a great adventure of survival and a process of survival of the fittest. Some birds that are weak or not strong enough can only be eliminated halfway, leaving birds with better genes.
Basic information of immigrants
Some birds can migrate regularly with the change of seasons in 1 year to change their habitats. This kind of bird is called migratory bird. Migratory birds can be divided into summer migratory birds and winter migratory birds. The former refers to flying to a certain area to nest and have children in spring and summer. When the young birds grow up, it is already late autumn. They fly to warmer areas in the south for the winter, and then fly to this area to breed in the next spring. For this area, this kind of bird is called summer migratory bird.
The first is physiological reasons. Every spring is the breeding season of birds, so migratory birds fly to the north in droves to find suitable breeding grounds and lay eggs to breed offspring.
The second is historical reasons. According to historical records, there have been many glaciers on the earth in history. After the glacier, the northern hemisphere is ice and snow, and the climate is extremely cold. Almost all insects were frozen to death, and birds living in the north were forced to leave their hometown and move to warm areas in the south. When the glaciers melted, these birds flew back to the north because of their nostalgia for their hometown. Due to the periodicity of glaciers, some birds have also formed the habit of seasonal migration.