Peterson, R. T, Trap-Lind, I, Mountford, G, Oordt, G. J. V, Tlcehurst, C. B, Aldotjs, A. E, Owen, J. H, Ford-Lindsay, H. W, Jones, R. W, Smith, J. B, Peterson, R. T & Robinson, H. W / November 1963 – vol. 56, issue 11–328 IT has long been known that, in the Common Crossbill (Loxia curvirostra) the mandibles cross indifferently on either side in different individuals. Recently, however, for a special purpose, I desired to ascertain whether or not individuals having the mandibles crossed to the right and to the left, respectively, exist in nature in about equal numbers, and (if not) what proportion of individuals ha... This article is only available to registered users.To read more, please log in or purchase a subscription.