Mechanical properties of mallard humeral bone in dependence on the form

The mechanical behaviour of bony material taken from humeral bone of the mallard duck was analysed. Wing-clipping led to a change in the values and distribution of the dynamic shear modulus and damping. The distribution of the values of the modulus shows a specific pattern in which the highest values are found ventrally. This pattern changes when there is a disturbance of the functional forces acting upon the humerus -- in this study induced by wing-clipping. The hypothesis is put forward that in birds the bone with its specific shape will resist any change in this shape. For a specific shape required for other functions than simply resisting load, it is functionally advantageous to respond to a change in required forces by adapting the pattern of moduli. An adaptation according Wolff's law will only occur in extreme cases, but an alteration of the bone shape will be avoided.