The Physics of Flight: World Bird Sanctuary in St. Louis

Bird of Prey -- at the World Bird Sanctuary.

A discussion of the physics of flight, interspersed with birds of prey swooping just centimeters from the tops of your head, made for a captivating presentation on avian aerodynamics by the people at the World Bird Sanctuary that’s just west of St. Louis.

Lift

The presentation started with the forces involved in flight (thrust, lift, drag and gravity). In particular, they focused on lift, talking about the shape of the wings and how airfoils work: the air moves faster over the top of the wind, reducing the air pressure at the top, generating lift.

The shape of a bird's wing, and its angle to the horizontal, generates lift. Image adapted from Wikipedia User:Kraaiennest.

Then we had a demonstration of wings in flight.

Terror from the air.

We met a kestrel, one of the fastest birds, and one of the few birds of prey that can hover.

Kestrel.

Next was a barn owl. They’re getting pretty rare in the mid-continent because we’re losing all the barns.

Barn owl.

Interestingly, barn owls’ excellent night vision comes from very good optics of their eyes, but does not extend into the infrared wavelenghts.

Barn owl in flight.

Finally, we met a vulture, and learned: why they have no feathers on their heads (internal organs, like hearts and livers, are tasty); about their ability to projectile vomit (for defense); and their use of thermal convection for flying.

The ground warms when it absorbs sunlight (e.g. parking lots in summer) and in turn warm the air near the ground. Hot air rises, creating a convection current, or thermal, that the vultures use to gain height.

The Sanctuary does a great presentation, that really worth the visit.