Ising's Theory of Bird Orientation

Abstract

THE orientation of birds on migratory and homing flights stillposes such baffling problems that the publication of an entirely new theory is a matter of exceptional importance to ornithologists. Critical experimental work on the homing of wild birds under conditions such that all guidance by-previous knowledge of topography is ruled out, is still all too sparse. Nevertheless, evidence has for a long time been slowly accumulating that some species at any rate must possess powers of orientation independent of any terrestrial landmarks (see Griffin, 1944; review¹); and more recently Rüppell² has added a further substantial piece of evidence for some ‘sense of direction’. But what sensory mechanism could enable the bird to estimate correctly experimental displacement and maintain direction ? For clearly any sensory equipment which is to meet fully the needs of the homing or migrating bird under adverse conditions, as when familiar landmarks are absent or obscured, must at least provide information with regard both to direction and latitude.