Scaling of skeletal element mass in birds.

The dry mass from different skeletal elements of 63 specimens belonging to 49 species of birds was measured. The body mass range was 5.7 g-98 kg. Correlations of the mass of the skeletal elements to body mass were established by means of Model II of regression. Positive allometry was found in the case of the femur, tibiotarsus-fibula, tarsometatarsus, synsacrum and thoracic vertebrae, while the skull and sternum showed negative allometry. For a given body mass, a larger mass of avian humerus, ulna-radius and tibiotarsus-fibula can be expected, in comparison with the corresponding bones in mammals. Finally, some species displayed special values for some of their skeletal elements. For example, two orders (Galliformes and Columbiformes) displayed a tendency to lighter skeletal structures.