Deficiencies in wing loading can be compensated, up to a point, by how rapidly a bird flaps its wings. Birds with small wings relative to body size, such as ruddy ducks, have high wing loading and must beat their wings rapidly to stay in flight. But ducks with larger wings in proportion to body size, such as mallards, have low wing loading and can beat their wings more slowly and still remain airborne.
The shape of a wing is also important, whether it belongs to a bird or an airplane. Air goes above and below the wing during flight. Air flowing over the upper surface of the wing has to move farther than the air flowing under the wing. In order for the two air flows to reach the edge of the wing at the same time, the air flowing above the wing must go faster, creating lift.
Takeoff and cruising speed are dictated by the aspect ratio of a bird’s wing. Aspect ratio is wing length divided by wing width. Mallards and other puddle ducks have a lower wing aspect ratio than many diving ducks. Because a puddle duck’s wings are typically large in relation to body size and have a lower aspect ratio, most puddlers can spring into flight and make sharp turns.
Puddle duck wings, however, are less efficient for achieving sustained high-speed flight. Since a diving duck’s wings have a higher aspect ratio and are smaller in proportion to body size and weight, divers have to run across the water to take off and must flap their wings more rapidly to achieve flight. High-aspect wings allow diving ducks to attain faster flight speeds than most puddle ducks but do not afford maneuverability in tight spaces.
The size and shape of a wing give it different aerodynamic properties, which in turn give birds varying flight capabilities. Since all ducks have high-speed type wings, they must flap nearly continuously, regardless of wing size. While this is the most energetically expensive form of flying, it is also the most reliable for species that make long-distance migrations. Ultimately, wings enable ducks and other waterfowl to take off, sustain flight, and exploit specific habitats, all of which have important consequences for their survival.
Michael Checkett is a biologist and communications specialist at DU national headquarters in Memphis. Visit his blog at www.ducks.org/checkettout