What do birds use to navigate

While this cue may be relevant for reed warblers and other migratory songbirds, it is by no means the only navigation system used by birds. Other birds, including seabirds and homing pigeons, have been shown to require olfactory cues scents and smells to navigate. And, while we are closer to understanding the mystery of how birds navigate using magnetic cues, it still remains something of a mystery as to how they sense the magnetic field.

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This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together. Please use a genuine email ID and provide your name. Read more: Migrating birds use a magnetic map to travel long distances Regardless, if birds have learned that magnetic intensity increases as they go north, they should be able to detect their position on the north-south axis wherever they happen to be.

The European robin is a stalwart of studies into the in-built "living compass" birds may use to orient themselves using the Earth's magnetic field. One chemical contender is a molecule in the retina of the eye known as a cryptochrome. The Oxford team studied a purified form of the molecule in the lab to see whether it was fit for purpose as a magnetic sensor.

They found it had the ability to form pairs of "radicals" that have high magnetic sensitivity. A radical is an atom or molecule that is highly chemically reactive. Prof Hore said the mechanism they have been investigating involves magnetically-sensitive chemical reactions initiated by light inside the bird's eyes - in their retinas, to be precise.

It's thought that light striking the retina causes electrons to move within the cryptochrome molecule, triggering the production of a pair of short-lived high energy radicals, which act like microscopic magnets.

Now, though, scientists have come up with a possible method based on a series of complex photochemical reactions that can occur within the eyes of birds, as well as other animals, which could help them use an internal compass. Professor Peter Hore, a physical chemist at Oxford University, explained: "Because the Earth's magnetic field is so weak, many people found it difficult to understand how it could affect bird or animal sense organs in a way that would help them to navigate.

Birds may use similar chemical reactions in their retinas, where photochemical reactions could lead to nerve signals which help them to orientate. Scientists have shown that animals can use a variety of cues to help them migrate long distances and return to the same breeding or feeding grounds.

These include visual landmarks, the position of the Sun in the day or the stars at night, and even the smell of specific locations en route. But over the past few decades, scientists have found that animals ranging from birds and mammals to sea turtles and even insects can use the Earth's magnetic field either as a compass to orientate themselves in a particular direction, or as a map to help them determine their location.

One suggestion is that animals do this by using an iron-containing molecule called magnetite which orientates according to the north-south direction of the Earth's magnetic field, in much the same way that a compass needle always points to magnetic north.