‘The mechanisms of avian orientation are not fully understood.? In species that migrate in flocks, including ducks and geese, experienced birds may guide juveniles from breeding grounds to winter grounds and back again.? Birds are know to inherit an endogenous programme for migratory activity; to navigate using solar, magnetic and stellar compasses; and to pilot by familiar landmarks.? It has also been suggested that they find their way by reference to winds, smells, infrasounds and minute changes in gravity and barometric pressure.’
William Fiennes, ‘The Snow Geese’