Why do migratory birds not always stay in the South but have to 'work hard' to fly to the North when the cold season is over?

According to the bird conservation organization Audubon, there are at least 4,000 species of migratory birds in the world, accounting for about 40% of all bird species on the planet. Although humans have documented the north-south migration of many birds at least 3,000 years ago, there's still a lot we don't fully understand about this interesting behavior.

Some of the most prominent migratory birds include cranes, turtledoves, and swallows. In addition, arctic terns are famous as true "biological planes" when they can fly from the North Pole to the South Pole in the winter in the northern hemisphere - all of which are their breeding grounds. With that ability, they can spend up to 2 summers per year.

Migratory birds make up about 40% of all bird species on the planet.

Why do birds migrate from the north to the south?

Contrary to previously thought, birds migrate not to escape the cold. Simply, if we look at the Arctic terns like the example above, we will see that their destination is Antarctica - which is as cold as, or even more, than the Arctic region, so the point of view is that birds need to avoid the cold in winter. winter is outdated.

In terms of evolution, all living things develop behaviors to adapt to living conditions and optimize energy use as much as possible. The question is, why do migratory birds "invest" enormous amounts of energy to fly tens of thousands of kilometers back and forth between the North and the South each year? Why don't they always settle in a certain location with abundant food and easy to survive?

Some birds simply migrate to warm tropics.

Food, energy and reproduction are the keys that scientists are relying on to decipher this interesting behavior in birds.

First, it's a fact that winters in the Northern Hemisphere are generally quite harsh. It takes a lot of energy to stay warm, and food is especially hard to come by, especially when fruit, insects, worms and other invertebrates are the mainstay of their "menu".

Moreover, thanks to the tilt of the Earth, there is a contrast in seasons between the Northern Hemisphere and the Southern Hemisphere - when the Northern Hemisphere is winter, in the Southern Hemisphere is the warm summer, abundant food. Some birds simply migrate to warm tropics. Once they reach the southern "berths", the birds can enjoy a rich, abundant food source without spending too much energy keeping warm.

Two Arctic swallows.

At this point, the answer will begin to unravel. There are obvious reasons for them to accept such long round-trip journeys year round, facing numerous dangers (such as being hunted by humans) en route. While many animals do not choose to do this, in part because of their inability to travel as far, it is a survival tactic of migratory birds.

"Hard work" flies back and forth, but worth it!

But why don't they stay in the tropics all year round, warm and plentiful food? It turns out, despite the Hollywood movies or the songs and pictures of the tropics depicting, life here is not exactly paradise. First, it is clear that the tropics have an abundant food source, but the number of hungry animals is equally large.

Migratory birds, who come from far away, have to compete directly with these native species. Not to mention, the tropical environment is the perfect "incubator" for infectious and parasitic diseases.

The tropics have a large population of native bird species.

To face the "dilemma": the North is cold and poor, the South is fiercely competitive and prone to disease, they must develop a perfect countermeasure. Spring migratory birds do this brilliantly, as they timed the arrival of spring in the North - a burst of food, fruit and insects to return to. They take advantage of this period for reproductive activity.

A few more advantages are:

• 1. When they return, natural enemies such as foxes or bird-hunters experience a population decline over the harsh winters, so they can enjoy a safe, fertile breeding season.
• 2. Spring and summer in the Northern Hemisphere have significantly longer days than nights, giving the birds more time to feed their young. The higher you go to the higher latitudes, the bigger the difference - at the North Pole, the sun doesn't set for weeks.

If they stay in the tropics, this advantage is eliminated and as a result they will have to have fewer young.

In short, bird migration is a problem with many variables to solve, and with the miracle of evolution, over millions of years, they have developed the most optimal strategies for " investment" in energy and the ability to maintain the breed. They have to answer a multitude of questions: Is the journey worth it, what are the risks, what predators are there in the destination, what diseases are there, what species do they have to compete with (including humans)?

Swallow - "messenger" of spring.

With such a complex "equation", it is understandable that birds are probably more intelligent than we think. The problem is, climate change is most likely having a strong impact on these variables, causing their behavior to change.

Scientists have found evidence for that change. According to results from 2010, robins have migrated several weeks earlier than around 1990. Or, some species of ferns, instead of migrating to Latin America as before, no longer travel further. coast of the Gulf of Mexico, much further north.