Why do birds migrate? Is it really because they're afraid of the cold?

Hundreds of billions of birds migrate each year north and south between breeding grounds and wintering places thousands or even tens of thousands of kilometers away like a miracle of life. And we have to admit that bird migration is one of the most fascinating natural phenomena on the planet.

However, we humans know very little about why they migrate. Many people simply think that they migrated south to protect themselves from the cold of winter. In fact, this view has long been outdated.

With the in-depth study of scientists, we will see that the migration of birds is full of mysteries and challenge human understanding over and over again. And let's find out the first case.

Ancient murrelet is a very strange bird, its beak is like a sparrow, its body is like a penguin, its wings are like ducks and young birds look like chicks. The most different thing from other birds is that their legs are very close to the tail and have an upright posture.

However, they seem quite awkward. This bird flies about 8,000 km per year across the entire North Pacific region and between the United States and Asia.

They breed in western Canada, then fly thousands of miles across the ocean in Japan and South Korea to winter. It is also the only known bird throughout the North Pacific.

Birds migrate to avoid the cold of winter is not entirely true.

At first, people thought that migrating birds was to avoid the cold of winter , however, recent research has found that this is not entirely true. The places where this bird migrates from to its place of birth all have relatively similar temperate climates at the same time.

Theoretically, if they stay where they were born and winter, the climate shield there does not matter much and they can still survive normally.

So why do they still have to go on a long journey to migrate every year? In this regard, scientists still feel confused and can not find the answer.

However, this example clearly refutes the view that migratory birds are to avoid the cold of winter.

We know that migration refers to the large-scale movement of wildlife, but none of the migration has received as much attention from humans as birds do and Not all birds migrate.

We can divide birds into two types: resident birds and migratory birds . As the name suggests, resident birds refer to being in the same place all year round and not migrating.

For example, the species of chickens, they have the ability to fly weak. Most resident birds live in warm climates, but there are also upland and cold species, such as snowy birds in the Himalayas and Emperor penguins in Antarctica.

Summer migratory birds are birds that come somewhere in spring and summer and leave in the fall.

Migratory birds are birds that have certain migratory behaviors. It is subdivided into winter migratory birds and summer migratory birds. Winter migratory birds refer to birds that come to a certain place to interweave in the winter and leave in the spring, such as swallow, swans and wild ducks .

Summer migratory birds are birds that come somewhere in spring and summer and leave in the fall. During this period, they often took the important responsibility of maintaining their lineage, such as cuckoos and golden sparrows.

But the difference between migratory and migratory birds is not absolute . The same birds can migrate to different areas and they may even abandon migration or vice versa. For example, the Sarus Crane was originally breeding in Hokkaido, Japan as a migratory bird, but over time, a number of Sarus Crane gave up the migration instinct and became a resident bird;

Another example is the drongo, which is a bird that lives on Hainan and Yunnan islands in southern China, but one of them migrates to the Yangtze and North China watersheds. by a fixed time of year.

So, what exactly determines the migration of birds? Why did some birds migrate last year, but this year they became northern birds for the winter?

Some scientists have speculated that bird migration may have originated during the ice age of 10,000 BC. When the ice season in the Northern Hemisphere and snowfall, some birds are forced to leave their habitat to find better living places to find food. When the cold passes, they will return to their previous home.

But as the winter season struck again, year after year, the migratory bird group gradually expanded and eventually formed the annual migration of migratory birds.

In other words, the glaciers' periodic erosion and freezing cause birds to form a permanent genetic instinct from generation to generation.

However, this theory still has certain gaps. It cannot explain why some birds did not migrate, and the ice age accounted for only 1% of the bird's survival history. Why is there such a genetic impact on birds in such a short time?

In recent years, two scientists, W. Alice Boyle and Courtney Conway of the University of Arizona, have come up with new ideas to study bird migration.

The reason why migration occurs is because of food shortages that occur in some areas during cold weather , forcing them to leave their homes and move to areas with high temperatures and abundant food. than.

They built a "genealogical super tree" showing the exact evolutionary relationship between different species. The computer then determines whether a particular species migrates according to "family traditions" or that their habitat changes and forces them to fly away seasonally.

When the cold passes, they will return to their previous home.

The researchers believe this new hypothesis could also be applied to most birds. Take the northern hemisphere for example, the northern part of the northern hemisphere is suitable for bird breeding in the summer. At this time, the temperature in the south is too high and the impact of human activities is quite large so it is not suitable for the majority of birds to mate but also to breed and raise young.

However, in the winter, the birds are facing major survival problems due to snow and ice in the north, so they will choose to move south. This hypothesis also explains why the same bird can switch between residence and migration.

If food in the north remains plentiful even at low temperatures, they will not hesitate to stay in the winter and migratory birds become resident birds. But if there were no winter food in the north, they would choose to move south for survival.

The reason why the Sarus Crane - the aforementioned species has changed from migration to residence - is that local people in Japan have provided them with a stable food source in the winter.

In warm areas, birds will have many natural predators and great competitive pressure.

So why aren't birds in warm areas with ample food all year round?

Although the equatorial regions are warm throughout the year and there is no shortage of food, there are many natural enemies and great competitive pressure . As the north warms up, the north also has more food and less natural enemies than the equatorial area, so the birds will fly back.

Some researchers believe this may be related to the different wintering and breeding environments of different birds . For small forest birds that do not migrate in the winter, they can change their diet from insects, fish, amphibians to grass seeds and berries on the snow.

Today, under the impact of climate change, human influence and other factors, the distribution range of some bird species has changed globally, and new migration behaviors are also shaped. into that.

1. Birds migrate at night in dispersed herds
2. The mystery about the ability to determine the longitude and latitude of migratory birds