An acquaintance asked me this question today. Can anyone give me a detailed
explanation of the aerodynamics of birds?

>Out my window I can see whitecaps aplenty, all heading southeast. There's
>obviously a strong wind (20-30 mph) from the Northwest.

>There's also lots of seagulls. Flying northwest. Without flapping their
>wings! Oh, there's few half-hearted wing-flags once in a while, but mostly
>they "glide" *against* the wind. I've noticed the same on the ferry. A
>seagull can "ride" a ferry going top speed by gliding alongside or above it.

>I'm beginning to suspect that just as a plane achieves lift by the
>difference in pressure between the lower and upper surface of the wing, a
>seagull achieves forward motion by a difference in pressure between the
>front and rear surfaces of its torso. Giving it thrust.

>How else can a bird glide forward against a strong wind?

>Or does the bird perhaps use a "tacking" motion. And never flies directly
>into the wind?

Thanks,

Tom Benedict
tbenz at halcyon.com