I believe that many people mention the animal "swallow". The first thing that comes to mind is "Little swallows come here every spring. I ask why the swallows come here. The swallows say that spring is the most beautiful here." This animal is swallows. It is still very common in rural areas. It is easy to see their nests under some eaves. Some naughty little boys even go up to dig out bird eggs. Then the question arises, why do swallows need to be in cold weather every winter Fly to the south, and then fly back to the north when the weather is warm. Wouldn't it be better if they stay in the south?

As we all know, in the north, starting from mid-October every year, the weather will gradually cool down, and it will slowly enter a very cold winter. For humans, we can get warm Over the winter, some animals can only rely on hibernation or other ways to survive the winter due to their relatively low evolution.

The swallow itself is a migratory bird and has the characteristics of a migratory bird. The migratory bird is a relative concept. For us northerners, the swallow is a and a summer migratory bird Swallows fly away in summer and return. For people in tropical regions, swallows are migratory birds in winter. Swallows fly away in summer and only fly back in winter. What's most admirable is that swallows themselves are just like carrying "GPS". They migrate every year. The route is fixed, and they can even find their old nest to live in for a long distance. Even if the old nest is uninhabitable, they will rebuild the nest near the old nest. Perhaps, this is a diehard fan!

Some people say that the swallow is a very stupid bird. It is a waste of time and energy to migrate back and forth every year. The south is not so safe and has all kinds of ferocity. The birds of prey, which also led to the excessive number of birds in the southern region, fierce competition and extremely high mortality rates, in fact, the little swallows flying back to the north are really "forced."
First of all, most plants in the north are deciduous forests, and insects are basically dormant or dead in winter. This also leads to a sharp decline in the food sources of the little swallows, so that even if they stay in the north, It is impossible to obtain enough food to maintain the population, but if human factors feed food regularly, even if it is migratory birds, they are not willing to fly to the south in winter, but prefer to stay where they are.

In addition, little swallows are warm-blooded animals. The weather is cold in winter. If they insist on staying in the north, they will consume more heat to maintain their body temperature. Although migration will consume a lot of energy , But if compared with the energy of staying in the north to spend the winter, it is definitely more cost-effective to migrate, so the small swallows flying far to the south or places with higher temperatures in winter will help them survive.
At this point, some people will say that since the south is better after weighing the pros and cons, why does it fly back to the north? Some zoologists said that it is normal for swallows to go back and forth between north and south. Swallows are very smart. They will choose to follow the revolution of the earth, that is, as long as they fly in a warm direction, the swallows can fly all over the world to find them. summer.

Moreover, swallows migrate long distances back and forth like this is a very smart behavior. It is necessary to know that swallows are inherently difficult to deal with powerful natural enemies. If they live in one place for a long time , Then you will be suppressed by natural enemies, but if you frequently migrate, this can effectively avoid fierce natural enemies, which can be regarded as a self-protection operation.
.-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-