As the earth spins, the stars appear to rotate. To an observer, the stars over the geographic North Pole or South Pole move the least, while those over the equator move furthest or fastest during the night. Experiments show that migratory birds use this as a cue to guide them in a constant direction. In this southern hemisphere view, to travel south a bird would fly towards the horizon in the direction of a point vertically below the centre of rotation (to the right of the centre of the horizon in the photograph).
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Mt John Observatory, University of Canterbury
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