Skeletonderdelen van zeevogels (1): Sternum

The breastbone of a bird comprises a convex/concave basal plate and a perpendicular keel ventrally. The shape of the breastbone is related to the species’ lifestyle. Foraging strategy, aero- and aquadynamics and gravity play important roles. Species with soaring flight and a low wing load generally have a short breastbone with a rather low keel and small pectoral muscles. When the wing load increases, and wingbeats become deeper and flight is combined with wing-propelled diving, breastbones are larger. In diving species, the breastbone is longer to protect the intestines from high water pressure. In wing-propelled divers the keel is considerably larger than in foot-propelled species. Larger species, that have advantage of a low wing load, mostly have pneumatic cavities in the breastbone. The true divers have solid bones to reduce buoyancy. The shape of the breastbone is a compromise between determining factors and shows considerable variation.