A Little Closer to Heaven: Sanibel birds on the Wing

All of us who live, work and play on Island, have our eyes up much of the time we are here.

We look at the clear blue skies, the brilliant sun and , often, the birds that use our little tropical paradise as a permanent or temporary home.

But those wings that we observe carrying our feathered friends from place to place are not just beautiful, they are extremely functional.  That is especially true for the larger birds.  The Great White Egrets, Woodstork, Anhinga, Cormorants and a host of others have multiple uses for their beautiful wings.

Birds adopt characteristic poses in which they extend and often slightly droop their wings. This behavior is commonly described as "sunbathing" or "wing-drying." Cormorants and Anhingas frequently assume these postures, which are also seen in both Brown and White Pelicans, as well as in some storks, herons, vultures, and hawks.

Spread-wing postures may serve different purposes in different species. Anhingas, for example, have unusually low metabolic rates and unusually high rates of heat loss from their bodies. Whether wet or dry, they exhibit spread-wing postures mostly under conditions of bright sunlight and cool ambient temperatures, and characteristically orient themselves with their backs to the sun. Thus, it appears that Anhingas adopt a spread-wing posture primarily for thermoregulation -- to absorb solar energy to supplement their low metabolic heat production and to offset partly their inordinately high rate of heat loss due to convection and (when wet) evaporation from their plumage.

Cormorants, in contrast, apparently use spread-wing postures only for drying their wings and not for thermoregulation. Although cormorant plumage also retains water, only the outer portion of the feathers is wettable, so an insulating layer of air next to the skin is maintained when cormorants swim underwater. This difference in feather structure may explain why cormorants can spend more time foraging in the water than Anhingas, and why cormorants can inhabit cooler climes, while the Anhinga is restricted to tropical and subtropical waters. 

Some birds, like the Great Blue Herons will open up their wings on a hot day, allowing air to circulate across their bodies and sweep away the excess heat.  Great Blue Herons will also "droop" their wings in addition to opening them to protect nestlings from the sun.

And then there are the wonderful workings of the large winged Wood Storks who will forage in the water for crabs , snails and fish while keeping their wings fully extended to see what is available in the sun lit estuaries and rivers.  Many other birds can be observed doing the same with their wings utilized for shading.

Spread-wing postures appear to serve for both thermoregulation and drying in Turkey Vultures. These birds maintain their body temperature at a lower level at night than in the daytime. Morning wing-spreading should provide a means of absorbing solar energy and passively raising their temperature to the daytime level. Field observations indicate that this behavior is associated with the intensity of sunlight and also occurs more frequently when the birds are wet than when they are dry.

So the next time you see a special Roseate Spoonbill sail across the sky, remember its expansive pink wings have many other uses....if in fact your awe does not get in the way of your memory!