Why do Anhingas spread their wings?
The answer may surprise you — it has nothing to do with oil glands or wetness. The structure of cormorant and Anhinga feathers decreases buoyancy and thus facilitates underwater pursuit of fishes. Hence, their plumage is not water-repellent, but “wettable.” It has been suggested that the functions of the spread-wing postures in these birds is to dry the wings after wetting. 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. In addition to helping wing feathers to dry, other suggested functions for these postures include regulating body temperature (thermoregulation), realigning of feathers, forcing parasites into motion to ease their removal, and helping the perched bird to balance. Spread-wing postures may serve different purposes in different species. Anhingas, for example, have un
