When will the swallows fly back to the north?

Swallow migration is mainly related to adequate food. Every autumn and winter in the north, insects will die in large numbers or get into the soil because they can't stand the cold, so that swallows can't find enough food to survive in the north in winter, but birds like sparrows who eat plant seeds can stay. So every autumn and winter, swallows fly from the north to the south and spend a winter with plenty of food and clothing. In the past winter, insects in the north have all recovered and appeared in large numbers. This is the time when swallows breed, so every year from April to May, swallows will rush back to the north, nest and breed in the north, and make a living by catching insects.

Swallows in the south are not worried about food because they are in the south, so they rarely migrate back and forth, and they are familiar and comfortable in the south. Swallow migration itself has little to do with temperature, but mainly with food.