The skeleton of the bird (Fig. 1 3.1) is unlike that of any other group of animals and it has developed from the evolution of powered flight.

Λ combination of a reduction in the total number of bones and the fusion of many joints has resulted in a skeleton which pro­vides a strong base for the attachment of the flight muscles. Although the skeleton must be light enough to enable the downward force of the wing to lift the bird into the air and to keep it airborne, when com­pared to mammals of a similar size birds are not exceptionally light.