Scientists say migrating birds rely on the magnetic compass after sunset. They also use the individual stars for navigation at night. All animals with “camera eyes”, the kind of eyes humans have, can make out individual stars. Insects with compound eyes cannot do this so they see the starry sky and the Milky Way as patterns of light. But scientists do not have an answer for one question: how do birds flying at night change the point of reference when they cross the equator? How do they follow the stars that change their orientation across the equator?
One example of birds that understand stellar navigation is the indigo bunting of North America. These birds fly south for winter, and they do it at night. There is less competition for food at night and there are fewer disturbances after dark. In one experiment, researchers captured these migrating birds and placed them under a starlit dome. And this is what they found.
Indigo buntings watch the rotation of close star patterns around a centre point, such as the North Star. From this they determine the directions. Before migrating, songbirds orient themselves by hopping in the direction they want to travel. In the experiment, the starlit dome rotated around the North Star, which is what happens in the night sky. The smart birds observed it and began to fly south. Then the researchers removed the constellations within 35 degrees of the North Star. The birds became disoriented and couldn’t fly anywhere.
So, individual stars are not that important for the birds. What they need to see is the rotation of the close star patterns around a centre point. This helps them to determine where north is. They use this information to fly south.
Picture Credit : Google