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Sunday, March 31, 2013

Preening

Preen gland, also called Uropygial, or Oil, Gland, in birds, an organ located on the back near the base of the tail. Paired or in two united halves, it is found in most birdsSource: http://www.britannica.com

BR Preening, March 27, 2013, 6:31 PM by MV

Most birds have a gland called an uropygial gland that allows them to not only obtain their vitamin D3, but also may help them to ward off insects, improve their waterproofing, reduce bacteria, and help maintain the general health of their feathers, scales and beak. The uropygial gland is located dorsally on the bird’s back at the base of the tail and is covered by a bird's feathers until they preen (running their beak along feathers, scales, skin, etc. to clean, straighten, or move their feathers).  The bird touches the gland with its beak, which releases the oil that the gland produces.  The gland has two lobes that may sometimes (depending on the bird species) have a ring of down feathers surrounding the opening (a nipple-like structure called the papilla) which acts as a wick for the oil it secretes.  When a bird moves to touch the gland, the bird lifts the covering feathers out of the way, since it can control groups of feathers.  A bird may then spread the oil throughout its feathers with its beak.  Some birds can rub their heads and feet on the gland as well.

The oil secreted from the uropygial gland contains vitamin D precursors and when exposed to the ultraviolet part of the sun’s light, is then altered to vitamin D3. When the bird preens its feathers again, it ingests the vitamin D3 from the oil. Isn’t Mother Nature amazing?

Source: Teresa Aldrich, World Bird Sanctuary Naturalist/Trainer. Read the whole article here.

 

Information compiled from a recent chat
conversation with Charles Eldermire,
Cornell Lab of Ornithology Multimedia Manager

  • Preening has several functions, ranging from essentially "brushing" the feathers so that the microstructure of the feathers stays properly maintained.
  • Preening also applies oils from the preen gland that can reinforce or condition the feathers' surface.
  • Some studies have even shown that the oils themselves change in composition across the year so that different oils are being applied prior to migration than during the breeding season, for example.
  • Preening puts the barbs and barbules back together if they get separated.

Lastly, Thor Hanson explains in his book, Feathers, The Evolution of a Natural Miracle, how it is the structure of the feathers themselves, not the oils, that contributes most to waterproofing. See recent blog post about this book here.

To see a photos of uropygial glands of a red-tailed hawk and some other raptors from The Modern Apprentice, click here.