Why do swallows fly from the south to the north every spring?

Because swallows feed on insects, they have always been accustomed to preying on flying insects in the air. They are not good at searching for insect food in cracks in trees and ground. They can't omnivore berries and seeds and eat leaves in winter like grouse and Thunderbird (some conifers don't shed leaves even in winter), and they can't dig up larvae, pupae and eggs of latent insects like woodpeckers and woodpeckers.

There are no flying insects for swallows to prey on in winter in the north, so they migrate.

Animal migration behavior is an adaptive phenomenon. With this activity, the environmental conditions they need in a specific life period can be met, and the survival of individuals and the prosperity of races can be reliably guaranteed.

Extended data:

First, the life habits of swallows

Swallows are most willing to approach humans, and humans also love this beneficial bird. Generally, they return to farms near farmland (insects) for breeding from April to July. Domestic swallows nest under the eaves of farmhouses. Most of these nests are made of saliva-bonded soil and grass stalks, covered with soft weeds, feathers, rags and so on. And some Artemisia annua leaves. The bird's nest is dish-shaped.

Breeding 2 nests every year, mostly from May to early June and from mid-June to early July. Each nest lays 4 ~ 6 eggs. The second nest is less, 2 ~ 5 pieces. Eggs are milky white. Males and females hatch eggs together. 14 ~ 15 days, the young birds hatch and are fed by their parents together. The chicks fly out in about 20 days, and then feed them for 5 ~ 6 days, so they can feed themselves. The food is full of insects.

The golden waist swallow is similar in shape to the domestic swallow, but slightly larger. This swallow has a chestnut waist, which is very eye-catching, and a small black line in the lower body, which is easy to distinguish from domestic swallows. Habits are similar to those of domestic swallows, but most of them live in mountain villages. Yan is a typical migratory bird. After the breeding, the young birds still follow the adult activities, gradually integrate into the large group, and move south for the winter before the first cold wave comes.

Second, the origin of bird migration

1. Birds originated in the south. As the continental plate drifted from south to north, many birds were brought to the north, so it became a habit for bird migration to try to return to their hometown in the south.

2. Birds originated in high latitudes, and the invasion of Quaternary glaciers from north to south forced birds to migrate to the south. When the glaciers retreated in summer, birds could regularly move back and forth between breeding grounds and wintering grounds, thus forming a migration behavior;

3. Birds originated from tropical forests in the south, and a large number of people multiplied, resulting in an increase in the demand for food. Therefore, ecological pressure causes some birds to spread to the places where glaciers retreat to the north in summer. When glaciers come and go back to the south for the winter, over time, they form regular migration behavior.

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