A new study led by researchers from the University of Oxford and in collaboration with scientists from the University of Oldenburg has shed light on how migratory birds navigate their way to their breeding site after flying across continents.
The international collaboration between the two institutions showed that these birds are using the Earth's magnetic field to tell them where and when to stop migrating. This trick allows them to precisely go back to their breeding sites every year after traveling thousands of miles away.
Magnetoreception: When Birds Use Earth's Magnetic Field As Stop Signs
According to Science Alert, birds use a biological tool called magnetoreception to know which way they are heading and to know which direction will lead them to their nesting sites. This often gives them an extremely accurate direction within meters of their original natal site.
The international team of researchers investigated whether birds may also be using Earth's magnetic field to locate these sites to see whether they know when to stop. Researchers said that the cues could be the magnetic inclination or the overall strength of the magnetic field.
The magnetic inclination is the dip between the magnetic field and Earth's surface, which researchers believe could be the cue that birds use during migration. Researchers hypothesize that the findings of the study point to magnetic inclination as a primary magnetic cue for the birds when they go back to their breeding sites, supporting their hypothesis that Earth's magnetic field serves as a "stop sign."
They suggest that birds lean the inclination angle before they depart from their breeding sites and recall its location using only one coordinate dimension. The findings also showed that yearly variations in Earth's magnetic are reflected in gradual positional changes of the nesting areas.
Why is Precisely Pinpointing Breeding Site Important?
The international team of researchers analyzed data from almost 18,000 reed warblers, which are tiny songbirds that fly across the Sahara Desert every year to spend the summer in Europe. According to Phys.org, researchers found that the magnetic sites to which the birds returned move along with the magnetic field. This means the birds were homed to a moving magnetic field.
The study utilized "ringing data" from nearly a century of uniquely numbered metal rings attached to the legs of birds. The ringing data gave scientists a fantastic way to answer questions about the migration of birds.
The team explains that magnetic information seems to be stable, which means that the magnetic field does not change that much in a given location. They noted that although trans-continental migration of birds is a remarkable feat, what makes it extraordinary is the ability of birds to accurately return to breeding sites from halfway across the world.
They hope their findings could inspire people to go out and watch birds and get excited by their behavior. The study titled "Magnetic Stop Signs Signal a European Songbird's Arrival at the Breeding Site After Migration" is published in Science.
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