Drag

Many features of a bird’s wing and body have evolved to minimize drag while maximizing lift. Drag is the unwelcome consequence of lift during flight. It is not possible to generate lift without drag—which slows the bird down and causes it to lose altitude.

Yellow-legged Gull (Larus michahellis) Texel Ferry, The Netherlands. May. Photographer: Peter Cavanagh

Yellow-legged Gull (Larus michahellis) Texel Ferry, The Netherlands. May. Photographer: Peter Cavanagh

Drag occurs in a number of ways: the gull above is experiencing “profile drag” because it is not offering a streamlined shape to the oncoming wind. During level flight, the flow over the wing surface causes “induced drag” as the air from underneath the wingtip wraps around to become a trailing vortex of turbulent air. Flow of air over all the surfaces of the bird also causes “friction drag”.

Northern Gannet (Morus bassanus) Bass Rock, Scotland. Photographer: Peter Cavanagh

Northern Gannet (Morus bassanus) Bass Rock, Scotland. Photographer: Peter Cavanagh

The Northern Gannet above minimizes profile drag in several ways. The beak smoothly blends into the head; the back and underside of the body are contoured; the tail is aligned with the body; and the feet are tucked tightly into the feathers. The wing surface is a smooth airfoil.

LEARN MORE ABOUT GULLS

KIDS QUESTION:

In the Museum exhibit we asked: How many different kinds of gulls can be found in the United States?

The answer is: Twenty-eight and they are sometimes hard to tell apart
There are 28 species of gulls can be seen in the United States Many gulls look alike. Careful examination of the colors of the head, legs, and feathers covering the upper wing will usually allow identification. However, juvenile gulls often look nothing like their parents until their 2nd or 3rd year.