Preening feathers is an important activity for many birds especially aquatic birds.. Birds rub their bill against an oily sac at the base of the upper tail feathers, called a “preen gland,” and distribute oil over their feathers. They adjust the feathers for flight and oil them for insulation. Oily feathers are especially beneficial for birds who have considerable contact with water.
Preening gland of Osprey
Preening Gland of Great Horned Owl
“Look at my preened feathers,” said Harriett.
“You can have feathers like this too, if you make the time, effort and use your uropygeal gland judiciously.”
“Everybody’s doing it!”
“You should try it,” recommended Harriett.
Osprey Tales 