Swallows are beneficial birds to human beings. They mainly feed on insects such as mosquitoes and flies. They can be eaten in a few months. Eat 250,000 pests, so we should protect them. Before winter comes, swallows always make their annual long journey - flying in groups from the north to the far south, where they enjoy the warm sunshine and humid weather, leaving behind the harsh frost and coldness of winter. The cold winds leave the chickadees, grouse and ptarmigans that never fly south for the winter. On the surface, it seems that the cold winter in the north causes swallows to leave their hometown and go to the south to spend the winter. When spring comes, they return to their hometown to have children and live and work in peace and contentment. Is that really the case? Not really. It turns out that swallows feed on insects, and they have always been accustomed to catching flying insects in the air. They are not good at searching for insect food in the gaps between trees and ground, and they cannot eat berries, seeds and other insects like oak grouse and ptarmigan. They eat leaves instead in winter (some coniferous species do not lose their leaves even in winter). However, in winter in the north, there are no flying insects for swallows to prey on, and swallows cannot dig out the larvae, pupae and eggs of hidden insects like woodpeckers and woodbirds. The lack of food forces swallows to make a great north-south migration from autumn to spring every year in order to obtain a wider living space. Swallows have become the "nomads" in the bird family.
