Wednesday, September 16, 2015
It’s Windy Out There
Almost every day after each of the World Bird Sanctuary Stone Zoo bird shows, one of the staff gets asked how much Norbert our Bald Eagle weighs.
Norbert, the Bald Eagle (photo: Sandra Lowe)
Usually we respond with a question, asking kids and adults how much they think he weighs. The answers are almost always higher than 20lbs, because most people don’t understand bird anatomy (Norbert weighs just 7 pounds).
The reason for this faulty weight perception is twofold; the first is something that’s not visible to the naked eye. Unlike we mammals, birds have hollow bones! The second reason is one that we can easily see, but usually don’t take into account when doing our weight calculations—feathers! Feathers are very lightweight—even though there may be several thousand of them on a bird such as an eagle.
Let’s talk about feathers--that amazing adaptation that gives birds their beauty, insulates them from the heat and cold, and most importantly—allows them to fly. (Of course, there are some flightless feathered birds, but that’s a discussion for another day.)
Flight feathers are common to the majority of bird species. Birds’ feathers will help to catch air, which allows them to stay in flight. Their wings allow them to direct the air so that they can create lift. They also will use their wings to flap, soar, and hover, but that depends on what their wings are built for.
Diablo, a Tawny Eagle, has passive soaring wings (photo: Aurora Potts)
There are four different wing shapes. The first one is Passive soaring wings, which means these birds have long primary feathers (the outermost feathers on the wing). These long feathers, with slots between each of the outermost five, allow these birds to catch the upward movement of vertical columns of hot air called “thermals” and to fly higher in the sky. Some examples of these birds are eagles, hawks, and storks.
The second type of wing is the Active soaring wing. This means that these bird wings are narrow and long, allowing them to soar for long periods of time on horizontal wind currents. Examples of these birds are gulls, albatrosses, and gannets.
Another type of wing is the Elliptical wing. These wings are very good for a short burst of high speed flying. Crows, ravens and sparrows are some examples of birds that have Elliptical wings.
This American Kestrel is a good example of High Speed Wings (photo: Gay Schroer)
The last type of wing is the High speed wing. The birds in this category have long narrow wings, which allow them to fly very fast for a long period of time. Swifts, ducks, falcons and sandpipers are some examples of these birds.
As mentioned above, although all these birds are very different, they all have one thing in common... hollow bones, which allow them to be lightweight. This is a key factor to why birds are able to fly. Since birds are so lightweight, wind does tend to affect them while they are flying.
Riley the Barn Owl (photo: Aurora Potts)
At WBS’s Stone Zoo bird show in Boston we definitely have windy days that have affected our birds. For our Barn Owl, Riley, wind can cause him to have to flap harder and longer to fly through the wind to get from one trainer’s glove to another. Diablo our Tawny Eagle does sometimes get blown off course of his flight pattern on very windy days, but because he’s physically fit from all the practicing we do with him, he always fights through the wind to come back. Our Red and Green Macaw Rio actually is the exact opposite of my other two examples; she would rather wait for the wind to die down, then fly.
Rio, the Red & Green Macaw (photo: Aurora Potts)
Those windy days can definitely make bird shows very interesting.