Re: Cormorants, anhingas & soaked feathers

["Jaime A. Headden" <qilongia@yahoo.com>]

Brian Lauret (zthemanvirus@hotmail.com) wrote:

<So I wonder, what could be the use of getting soaked to the skin and having to
dry up, what makes it such a succesful strategy and why could it have evolved
in the first place (or: why didn't waterproof plumage evolve in cormorants and
anhingas?>

  Likely they did not trap air under the feathers and thus were less bouyant.
The pelecaniform birds in question (Anhingidae and Phalacrocoracidae) may lack
a gland for oils used to "seal" feathers, thus the hours of preeing and sunning
before the next dive, but there would be no apparent selective pressure to do
so. While loons and grebes and ducks have repellant feathers, they are surface
swimmers, and thus expend less energy to dive down; they also dive less deeply
than the pelecaniforms, and can keep up repeated short dives or dappling
without much preening or re-oiling. Spheniscids spend nearly their entire lives
in the water, and thus waterproofing has a selective advantage for keeping the
birds alive. This is all I can think of, and some of this may have been gleaned
from _Mammalian Species_ and Walker's and Grzimeck's encyclopedias, but I can't
cite refs yet. Besides, I need a few hours of sleep....

  Cheers,

Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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