Great Cormorant (Phalacrocorax carbo) Science Article 28
This paper describes an investigation into the factors influencing the occurrence and duration of the wing-spreading behaviour of the Cormorant. It was found to occur only after a period in the water (that is, when the plumage was wet), and its duration to be inversely related to wind speed and the length of time spent in the water. In addition birds tended to face into the wind during wing-spreading and, at low wind speeds, away from the sun. The extent to which the wings were spread was also inversely related to. wind speed. The results are discussed with respect to five proposed functions of wing-spreading (wing-drying, thermoregulation, balancing, intraspecific signalling and as an aid to swallow fish) and it is concluded that they support overwhelmingly the wing-drying (or more generally plumage-drying) explanation, with the ultimate goal of conserving metabolic energy.
Sellers R.M., ARDEA 83 (1): 27-36.