How do they manage to do this? Most birds have remarkable memories and are good at "pattern recognition". Migratory birds usually fly using the position of stars, the sun, and star patterns. Birds also, of course, use landmarks, such as rivers, mountains ranges, coastlines seen during previous journeys as path guides.
But the most important environmental cue the bird used during its migration is the earth's magnetic field. Birds can measure the angle between the magnetic lines that surround the earth and the vertical direction of gravity; and take bearings from this 'magnetic dip'. The value of the magnetic dip at the nesting site is perhaps imprinted in the bird brain.
On its way back home after the winter sojourn, the bird flies in a direction which brings it closer to and ultimately exactly to this figure.
But the most important environmental cue the bird used during its migration is the earth's magnetic field. Birds can measure the angle between the magnetic lines that surround the earth and the vertical direction of gravity; and take bearings from this 'magnetic dip'. The value of the magnetic dip at the nesting site is perhaps imprinted in the bird brain.
On its way back home after the winter sojourn, the bird flies in a direction which brings it closer to and ultimately exactly to this figure.
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