Earth’s magnetic field is like a compass… but for birds


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  • We may have a clearer understanding of the physics driving bird migration patterns.
  • Scientific American recently explained how birds use the Earth’s magnetic field to guide their migratory journeys, and there’s a lot of hard science — including quantum mechanics — involved.
  • There is still more to learn about how birds use their environment and biology to migrate successfully. Maybe being “bird-headed” isn’t so bad after all.

    Just as the ancient Minoans of Crete used the stars for sea navigation, birds today use the earth’s magnetic field to migrate.

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    Black-tailed godwits — famous for their longest-known uninterrupted migratory journey — use the magnetic field to help them figure out their current location and figure out where to go next. And while this isn’t the first time scientists have studied mangetoreception (also called magnetoception) in birds, we still don’t have a clear understanding of how these animals are able to tap into and use the magnetic field.

    Black-tailed Godwit, Scolopacidae
    black-tailed godwit.

    DEA / C. GALASSOGetty Images

    Corresponding Scientific Americanbut we’re getting closer to solving the mystery that seems to begin with the eyes of our feathered friends. SciAm reports that birds can essentially “see” the lines generated by our planet’s magnetic field via a photochemical process that renders them hypersensitive to the radical pair mechanism – theoretically explaining why magnetic fields affect chemical reactions.

    Radical pairs are molecular fragments with unpaired electrons that rotate in either an antiparallel pattern (denoted ↑↓ and referred to as the singlet state) or in a parallel pattern (denoted ↑↑ and referred to as the triplet state). Basically, this means that birds have photoreceptors in their eyes that are sensitive to the photochemical reactions of radical pairs. This—along with skills inherited from their parents and an internal clock that lets them know when to migrate—enables the birds to successfully complete their journey.

    Research has also shown that a bird’s ability to detect a magnetic field might even rival a human’s ability to use a compass for navigation. Not only birds can do that see a magnetic field, but they can also detect the axis of the field and the angle it makes against the earth’s surface.

    digital illustration of bird migration navigation including sun, stars, coasts, earth
    Digital illustration of migratory navigation of birds including the sun, stars, coasts and earth.

    Dorling KindersleyGetty Images

    In addition, birds have two other tools to help them navigate: an internal compass that helps them analyze the position of the sun in relation to their location, and the scattered star pattern that is visible at night. In fact, many birds learn where “north” is by analyzing the movement of the stars in relation to Pole Star. Even a bird’s sense of smell is critical to a successful journey – it can tell from familiar scents whether it’s been somewhere or not.

    While this research tells us more about the mysterious mechanics of bird migration patterns, there is still much to learn. One thing we do know for sure is that birds are anything but Goodbird brain.

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