|Looking north-east from Westham Island bridge. A light sprinkling of snow on the hills, and five double-crested cormorants on a log.|
|They usually sit with their bills slanted upwards. I wonder why.|
|Drying his wings.|
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. ...
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. ... Thus, it appears that Anhingas adopt a spread-wing posture primarily for thermoregulation -- to absorb solar energy to supplement their low metabolic heat production ...
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.
(From Stanford Birds)
|I don't know why they "gargle".|