Question

The mallard duck possesses a keeled sternum. What is the function of this specialised bone structure?

• A. To provide stability in water
• B. To provide a site of attachment for the large flight muscles
• C. To increase the body's surface area for heat exchange
• D. It is a weapon used in sexual competition between males

Answer 1

The correct option is B To provide a site of attachment for the large flight muscles

A keel in bird anatomy is an extension of the sternum (breastbone) which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs.

In birds, the sternum (typically) has a keel-like projection to which the pectoral muscles attach; these muscles provide the all-important downstroke in powered flight. In contrast, flightless birds lack a keeled sternum -- if you don't have big, strong flight muscles, you don't need a keel to attach them to.