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or wishbone, an arc-shaped bone of the shoulder girdle of birds, formed by the connate clavicles.
The furcula may be connected to the sternum, while its upper ends are connected with the scapulae and coracoid bones. The furcula gives the shoulder girdle elasticity. This structure has existed since the time of the archeopteryx. It is well developed in birds that fly easily and less so in those that fly poorly. In some parrots and owls the furcula is not connate, but both its branches are connected by a fibrous ligament. In flightless ratite birds the furcula is rudimentary, and the clavicles are either not joined or absent altogether, as in the kiwi or the extinct moa.