Cormorant Close Up
by Lisa Kilby
Title
Cormorant Close Up
Artist
Lisa Kilby
Medium
Photograph - Photography
Description
Double-crested Cormorants are the most widespread cormorant in North America, and the one most frequently seen in freshwater. They breed on the coast as well as on large inland lakes. They form colonies of stick nests built high in trees on islands or in patches of flooded timber.
Some 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. The structure of cormorant and Anhinga feathers decreases buoyancy and thus facilitates underwater pursuit of fishes. Hence their plumage is not water-repellent, but "wettable."
It has been suggested that the function of the spread-wing postures in these birds is to dry the wings after wetting. Biologists once thought that deficient production of oils from the preen gland necessitate wing-drying behaviors. We now know, however, that the degree of waterproofing of feathers is primarily due to their microscopic structure, not to their being oiled. In addition to helping wing feathers to dry, other suggested functions for these postures include regulating body temperature ("thermoregulation"), realigning of feathers, forcing parasites into motion to ease their removal, and helping the perched bird to balance. 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. Web.Standford.edu
NOTE: The watermark in the lower right corner of the image will not appear on the final print.
FEATURES:
Wild Birds of the World 2/23/2017
Uploaded
February 22nd, 2017
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Viewed 146 Times - Last Visitor from Monmouth, OR on 02/29/2024 at 5:28 AM
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Comments (11)
Elizabeth Winter
I just love when these guys migrate thru Omaha. Love this portrait of the cormorant drying his wings! f/v
Morris Finkelstein
Wonderful close up photo of a Double-Crested Cormorant drying itself, with great colors, pose, light, details, and composition, Lisa! F/L
William Tasker
Hi Lisa! Your beautiful image has been featured by Wild Birds Of The World! L/F
Lisa Kilby replied:
Many thanks, William! Always an honor to be featured on this wonderful group's homepage! :)