While looking out the window during that recent December deep freeze, the house sparrows in our neighborhood demonstrated incredible precision in their frantic feeder flights. Sharp turns, high speed dives and abrupt landings were in order. Chickadees, with two of three quick wingbeats, followed by a glide, land gracefully on a feeder rim. How do birds manage such amazing flight?
When comparing the varied size of different bird species key ideas stand out. A combination of light weight, strength and shape, supported by precision control augment flight. Every wing part needs to give maximum power with minimum weight. The larger the bird, the bigger the wings and the need for larger muscles to move those wings. Although it looks like feathers grow all over the bird, they actually grow along feather tracks. In between the tracks are down feathers that help insulate and lighten the bird. Picture the hummingbird and the white pelican in flight sharing the skies!
The design of wings and feathers of course, although unique to each species, do share common features. Similar to hair, feathers made of keratin. Each feather has a follicle that forms the hollow shaft and feather vane. The vane consists of thousands of branches called barbs. These barbs have many spaces to trap air and ease flight.
When watching a bird, the feathers we see are contour feathers that provide the color and shape. Looking closely, you will see that feathers overlap one another to keep the body dry, shed moisture and insulate the bird. Birds control contour feathers with specialized muscles. Barbules on the barbs hook together to give birds that smooth look. Contour feathers make up the flight or “remige” feathers which are defined as primary, secondary and tertiary feathers. Furthest away from the body, the 10 largest contour feathers are primary feathers that allow the bird to fly. These feathers are not symmetrical, providing a stiff front edge to prevent twisting in flight. Mid back-of-wing secondary feathers go along the arm of the wing and help sustain flight. Tertiary feathers are the smallest, innermost feathers, closest to the body.
Tail flight feathers, called “retrices”, help a bird maintain control, stability and act as a rudder to turn and twist quickly in flight. These six pairs of feathers also act as a set of bird brakes for landing. Overlaying and bordering the flight and tail feathers are feathers called “coverts”. Coverts give the bird a streamline shape to minimize drag and help insulate the body. Downy feathers or “plumulaceous” feathers have long barbules and flexible barbs to help trap air to insulate the bird. Those are certainly ones very useful for all winter birds.
Feathers wear over time and need to be replaced. This process, called molting, is done by birds at different times, suitable to aid the long-term survival of its species. Isn’t flight wonderful? All is possible with the right feather’s.