Magnetic Fields Guide Migratory Birds
Quantum biology reveals magical details about animals with magnetic compasses...
Songbirds are known to carry a built-in magnetic compass and clock that help them to navigate.
They use these to to guide their migrations by using them to "see" the Earth’s magnetic field, but how?
Oxford Univerity's Joe Wynn wondered the same thing, and set up a study to explore which specific magnetic parameters, or cues, these birds are using.
Earth’s magnetic field changes by a small amount year on year. Over time, this could cause the birds to migrate to a slightly different places, but Wynn and his colleagues found out that this isn’t the case, so they must be compensating in some way.
Wynn realised that one consistent features of the planet's field is its inclination. In other words, the angle of the field relative to the Earth's surface. While the field itself may vary slightly, the direction in which it is orientated is much less variable and this is what the birds appear to look for.
But, there will be multiple places on the planet's surface where the inclination is the same: the field dips down at the same angle in the northern and southern hemispheres, so how do they avoid becoming disorientated?
According to Wynn, it's a mixture of prior knowledge and the ability to know the vague direction of home, superimposed on the signal from the field inclination. “Birds will be travelling along an already determined direction that they probably would have inherited genetically. They would be travelling in this direction and they would wait until they hit the magnetic inclination value that thought represented their home, and then they stop.”
Essentially, the inclination acts like a stop sign along the predetermined path the birds are following. The uncanny part is that they already know where they’ll be heading back to before they even leave!