Over the course of a year, a bird will encounter unpredictable conditions. At times unfavorable weather, such extreme temperatures or high winds, can ground the otherwise airborne animal. Certain birds of a feather prefer water, including waterfowl that visit and revisit the Rocky River year after year. Late this winter, as the Rocky River churned the 12-inch glaze of ice from its surface, pools of open water provided grebes, mergansers, and other dabbling or diving ducks with refuge. The river water, sourced by cold groundwater, was just as you’d expect, cold! How can birds tolerate such low water temperatures?
Birds are equipped with countless adaptations to improve their survival odds. First coming to mind, feathers. A wing of feathers provides the most unusual mode of locomotion, flight. Feathers also deliver displays of unique color patterns (plumage) for communication. And perhaps of overlooked importance, feathers efficiently provide thermoregulation. Feathers, offering so many adaptations, are of high evolutionary importance. It is for these reasons that a bird must protect their feathers.
Feathers are made of keratin, the same structural component of our nails, hair, and even skin! This fibrous protein is extremely strong and resilient to everyday wear and tear. Even so, protection and maintenance are vital. From the time that a feather develops, until it is shed for a new one during a molting process, it must be well-kept. There exists an oil-containing sack called the uropygial gland. It is internally located just above where the tail feathers connect to the bird. To note, not every single bird species is equipped with this gland, but the vast majority are. Have you ever seen a bird biting its feathers? What you likely witnessed is an effective maintenance behavior called preening. The bird is actually taking a small amount of oil, from the uropygial gland, and applying it along the feather blade (vane). This personal grooming technique improves feather integrity and among other things, waterproofing! The thermoregulatory ability and water repellency of feathers affords birds the option for a cold swim in the frigid Rocky River.
| Water from the frigid Rocky River rolls off this female mallard (Anas platyrhynchos) in early March. Her uropygial gland secretes oil applied during preening, to promote feather integrity and water repellency.
The next time you’re at Euclid Creek, Huntington, or Lakefront reservations, look for gulls bobbing in Lake Erie. You’ll notice that the water rolls off the body, leaving the gull dry. Certain ducks, diving ducks for example, will completely immerse their bodies under water while foraging for food. When the ducks emerge after the swim, they’re dry! If the feathers become wet, all of those crucial benefits are lost, including thermoregulation. And that’s why birds take such good care of their feathers.
-Marty Calabrese, Naturalist