![Graphic][1] No self-respecting 15th or 16th century explorer would leave home without one: magnetic compasses guided the great explorers as they voyaged into uncharted territory, and migrating birds are no… Click to show full abstract
![Graphic][1] No self-respecting 15th or 16th century explorer would leave home without one: magnetic compasses guided the great explorers as they voyaged into uncharted territory, and migrating birds are no different. Guided by two internal magnetic compasses – one that measures the angle
               
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