Preening
Running the bill along a feather in order to maintain it in good order. Disarrayed feathers are repaired by preening due to their barb structure; preening also spreads oil over the plumage, secreted by the 'uropygial gland' or 'preen gland' situated just above the base of the tail. Constant preening is required if a bird is to keep its feathers in trim for efficient insulation and flight.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver