Symmetry and precision of control of strength in limb bones of birds

Abstract

The symmetry of the mechanical properties of paired long bones gives an idea of the precision of formation of animal skeletons. We report results of tests on gulls (Larus fuscus), pigeons (Columba livia), and battery hens (Gallus gallus). The gulls show much greater symmetry than the other birds, and indeed greater symmetry than any of the animals reported in the literature, which are all domesticated.The implications of these findings for Alexander's (1981) theory of safety factors are discussed. We conclude that, in the wild, variability of load is much more important in the evolution of strength than variability of strength due to imprecise control of growth.