Each year, billion Birds migrate in and outside the United States. And around the world, birds travel thousands of kilometers to reach their seasonal destinations. Some birds, such as the Arctic Sterne (Sterna paradisaea), even accumulate enough kilometers during their lifetime to fly to the moon and back.
But when the birds embark on these epic journeys, how do they know where they are going?
Birds Have an arsenal of meaning they use to orient themselves – some that we know, and some are always beyond human understanding.
“We know that birds use a variety of clues to keep their migratory direction”, ” Miriam LiedvogelThe director of the Aviary Research Institute in Germany, told Live Science in an email.
View and smell are two basic clues that birds use to find their way. If birds have already migrated once, they will probably remember familiar monuments, such as rivers and mountain ranges. Birds that migrate on the water, on the other hand, have fewer landmarks to guide them. In these circumstances, they could count more on their smell; A study noted that when the researchers blocked the nasal passages of sea birds called scopoli’s shearwaters (Calonecris Diomedea), they could still fly over the land but became disoriented when they defeated above the water.
Birds can also use the sun and stars as guides. To do this, the birds flying during the day use one “Sun compass“which combines the vision of birds of the place where the sun is located in the sky with their internal perception of the hour of the day it is based on their circadian rhythm. artificial light preventing them from sailing with precision, showing the importance of the boom.
However, most birds migrateThis means that the position of the sun is little used to them. In this case, the birds rely on the position and the rotation of the stars to find their way. They use this Star compass by Learn the position of the stars Around the celestial post, which is almost marked by Polaris (the northern star) – the same star humans used to navigate for millennia.
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Magnetic fields
But what happens if the sky is cloudy and the birds cannot see the sun, the stars or the landmarks? It is at this moment that the more fantastic senses of birds come into play. Birds can find their way even without sun or stars, partly thanks to a meaning called magnetore conception. This meaning allows birds to perceive the magnetic fields of the earth, which are generated by the undulating melted metals in the heart of our planet. This feat can resemble science fiction, but research shows that playing with magnetic fields has a great effect on birds; For example, a study found that the modification of the magnetic fields around the pigeons disturbed their return capacities.
Although it is clear that birds are capable of magnetore conception, exactly how they do it is less certain. Peter HoreProfessor of chemistry at the University of Oxford, said that birds must use a sort of chemical reaction, the outcome of which depends on the strength and direction of the Magnetic field of the earth. There are a few candidate theories on how this reaction occurs, but the hore bet is on a molecule called Cryptochrome, which is present in bird retinas.
The researchers have confirmed in the laboratory that the isolated cryptochrome responds to the magnetic fields and that this reaction requires blue light, which has also proven to be necessary for the magnetore conception of birds. However, researchers do not know exactly how sensitive cryptochrome is to use tiny variations in the magnetic field of the earth.
“We know so little about the details of how this compass could work,” said Hore. “I mean, we don’t even know how many cryptochrome molecules there are in the retinations of birds.”
Certain research also points to a magnetotoreation mechanism inside birds. Studies have found receptors that interact with magnetiteAn iron -based mineral, in the upper part of the birds of birds. These receptors connect to the brain via important nerve pathways, suggesting that they could be another technique that birds use to assess the intensity of the magnetic field.
In addition to magnetore conception, birds can gain information on their direction by detecting polarized light – a type of light in which the waves oscillate in a specific and aligned plane. Sun light becomes polarized predictably when light disperses in the atmosphere of the earth. Using special cells in their retinas, birds can detect these models, which gives them information about the place where the sun is in the sky, even when covered.
Assemble the parts
Just as we count on our vision during the day, but can use our hands to guide us in a room weakly lit at night, birds use different meanings at different times.
“The birds probably integrate their compass indices to navigate – and we are almost sure that different indices are of variable importance during their trip,” said Liedvogel. Hore also underlined this; Magnetotoreption, for example, is less useful during thunderstorms or high solar activity periods, which can both disturb the magnetic fields of the earth, he said.
In the end, all these strategies are supported by the genetic will of birds to migrate. Birds inherit the propensity to migrate by their parents, said Liedvogel, and the distance and the direction in which they fly are mainly Genetics. Researchers like Liedvogel always study exactly which genes are responsible and how they work.
The two scientists said that understanding these systems would be essential in the future of bird conservation. The species of moving or rewilding birds have become a major objective of fauna conservation efforts, but so far, the results have been mixed; A analysis found that in 45% of the studies, the birds have left their new location.
“Human efforts to move these birds have not been much successful,” said Hore. “It is partly because they are so good browsers that if you move them, they just come back.”
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