Friday, November 26, 2010

Hung out to dry

We weren't planning to stop at Westham Island bridge; it's always cold and windy there in the winter. But then we saw the cormorants ...

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.
 Most water birds have "unwettable" feathers, so that they dive or dabble and come up dry. Cormorants' outer feathers, in contrast, are "wettable"; this may be helpful, reducing their buoyancy as they make long dives in pursuit of fish. Because of this, they need to air-dry their wings; the water doesn't just roll off. So they are often seen sitting with the wings spread out.

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".
The feather patterns are beautiful. It's worth your time to right-click - open link to get a good look at them.


  1. Nice photos and a very interesting read.

  2. Very interesting feathers, so pretty

  3. It is well worth it to see those beautiful feathers; thank you so much.I've been enjoying your blog and pics for some time now but don't think i've commented before.
    Keep up the good work; it's so very much appreciated.


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