by Caitlyn Johnstone
January 10, 2019
Bird feathers are a unique feat of precision engineering. They have to help a bird achieve peak performance in flight, be warm enough to protect from extreme weather and still be light enough to help a bird stay aloft.
The calamus, the part of a bird’s feather that was used as a pen long ago, is a hollow shaft covered in barbs, which are the individual feathery pieces that fan out of a single feather. Each barb is in turn covered in tiny barbules, which themselves have tiny hooklets, taking the feather features down to a miniature scale. This cross hatching design helps the feather stay strong and keep its shape, standing up to all the wear and tear of a bird’s daily life.
From soft, warm down feathers to aerodynamic flight feathers and rudder-shaped tail feathers, each one is designed to fit individual uses. On each bird’s wing, feather placement is different depending on how that particular bird will use it to fly, hover, swim or soar. You can learn to tell a bird species by individual feathers, but it can be particularly easy to identify a bird based on how it uses all those feathers together in flight.
If you are trying to identify a flying bird from the ground, watch for a wobble. The distinctive wobble of turkey vultures, where they teeter from side to side on their V-shaped wings, is a behavior called contorted soaring.
Turkey vultures rarely flap their wings, instead gliding along on drafts like a paper airplane. One wing is held mostly parallel to the ground, and the other tilted up. Fast-moving air flowing across the top of the parallel wing lowers the air pressure above the wing, so it is less than the pressure created from the slow-moving air underneath the wing. The higher pressure under the wing creates lift, keeping the wing up.
Turkey vultures have an impressive six-foot wing span, but unlike most large birds, they rely on their sense of smell rather than eyesight to find their prey. By staying lower to the ground, they are better able to smell out carrion.
As an added bonus, a lower altitude and staying closer to the tree line may keep them below the notice of black vultures, which are smaller but more aggressive than the turkey vultures. The problem with flying low is that a turkey vulture is a lot of bird to keep aloft, and there are fewer updrafts at lower altitudes. By continuously tilting to change which wing experiences lift, turkey vultures make use of small-scale air disturbances in distinctive style to keep on soaring.
Learn more about the birds of the Chesapeake.