>Cormorants seem like a rather independent lot, off the colony, with some air
>drying, and some not, with little or no interaction, so signalling appears
>unlikely to me. Do Cormorants have much of an oil gland? You (or at least
>I) don't see them preening like lots of other aquatic birds. Moreover, they
>don't seem to be as bouyant; most of their bodies are underwater when
>they're surfaced. Anhingas also hang their wings out to dry and don't
>appear very buoyant either.
>
>Herb Curl


There are some interesting tidbits presented in an essay in _The Birders
Handbook_ called "Spread-Wing Postures", pp. 25, 27.

In summary it says:

Cormorants and Anhingas frequently assume spread-wing postures, which are
also seen in both Brown and White Pelicans, as well as some storks, herons,
vultures and hawks.

The structure of cormorant and Anhinga feathers decreases buoyancy ...to
facilitate fishing... hence their plumage is not water repellent. It was
once thought that deficient production of oils necessitated wing drying, but
it is actually the microscopic structure of the feathers, not the lack of
oil that makes drying necessary.

Anhingas have low metabolic rates and whether wet or dry do the spread-wing
posture for thermoregulation. Cormorants do it for drying. Turkey vultures
do it for both reasons.

In additiion to drying and thermoregulation, spread-wing postures are used
for realigning feathers, forcing parasites into motion to aid in removal,
and helping with balance.


Bill and Nancy LaFramboise
Richland, WA
wlafra at oneworld.owt.com