There are many theories explaining this capability of birds. According to one of them, the Sun’s rays and the direction of winds help them to navigate. Birds’ extra sensory capabilities assist them in this task and direction them with the help of the Earth’s magnetic field.
Another theory suggests that these winged wonders understand star-maps so well that it helps them to rack their way. But no one answer has been put down for this as of now.
Birds have the capability to detect changes in atmospheric pressure, weather and earth’s magnetic field. Based on these they locate specific regions and find their home. But the most important navigational aid is said to be “internal magnetic compass” that they are said to posses in their brain. The compass works in relation to the earth’s magnetic field. The magnetic currents generated here are turned into flight paths.
As a result, disturbances in Earth’s field can seriously affect bird’s judgment. In July, 1998, 3000 homing pigeons that set off for their return journey from northern France to southern England could not reach their destination because an explosion on the surface of the Sun, a few days prior to their journey, had sent radiations that disrupted the Earth’s magnetic field. As a result their internal magnetic compass picked up confusing signals and the birds lost their way.