Earth's magnetic field plays a vital role in everything from animal migration to protecting the Earth from the Sun's harsh solar wind. Now, a recent study finally sheds light on how some birds visually see Earth's magnetic field. Birds use Earth's magnetic field as sort of a heads-up display to help them navigate the globe.
The Earth's magnetic field is a result of the movement or convection of liquid iron in the outer core. As the liquid metal in the outer core moves, it generates electric currents, which lead to a magnetic field. The continual movement of liquid metal through this magnetic field creates stronger electrical currents and thus a stronger magnetic field. This positive feedback loop is called the geomagnetic dynamo.
While scientists have known for quite some time that birds can see Earth's magnetic field, it was unclear exactly how birds are able to visualize the magnetic field. Two recent studies from researchers at Lund University in Sweden and Carl von Ossietzky University Oldenburg in Germany discovered that the ability is a result of a special protein in bird's eyes. The two papers studied European robins and zebra finches and found evidence for an unusual eye protein called Cry4.