CONTRIBUTION OF INTERNAL BONY TRABECULAE TO THE MECHANICAL-PROPERTIESOF THE HUMERUS OF THE PIGEON (COLUMBA-LIVIA)

Mechanical properties of the pigeon humerus are significantly influenc ed by internal bony trabeculae. Experimental testing of braced (intact trabeculae) and unbraced (trabeculae experimentally removed) humerus pairs extracted from the same individuals demonstrates that the flexur al rigidity, strength and toughness (work of fracture) of the pigeon h umerus are all augmented by an intact framework of trabeculae. Measure d differences in mechanical properties in braced/unbraced comparisons generally exceed discrepancies attributable to random variation in con struction and thus cannot be ascribed to inherent skeletal asymmetry. The structural contribution of bony trabeculae is apparently greater i n subadult birds, possibly due to thickening of cortical bone and/or i ncreasing mineralization of bone tissue with age.