HOMING EXPERIMENTS WITH STARLINGS DEPRIVED OF THE SENSE OF SMELL

Three hundred and forty adult European Starlings (Sturnus vulgaris) we re caught in nest boxes at a colony in southern Germany. Half were mad e anosmic by bilateral olfactory nerve section; the others were sham-o perated and served as controls. The birds were displaced over distance s of 30, 60, 120 or 240 km, respectively, either towards east or west. Over 30 and 60 km, both controls and anosmic starlings returned at a rate of 40-50%. Over the longer distances, the return rate of controls remained the same (120 km) or decreased only slightly (240 km), where as the percentage of anosmic homers was drastically and significantly reduced. The findings are analogous to corresponding results obtained with homing pigeons and strongly suggest that starlings also require p erception of olfactory signals for orientation to home over longer dis tances. Returning to the nest site in the following spring was also si gnificantly lowered by anosmia, suggesting that olfactory navigation i s involved in the seasonal migrations.