Feathers are a marvel of construction. Smaller birds tend to have around 900 while there are larger ones could even have around 20,000 feathers. Though we say as light as feather, they make up a surprisingly large proportion of most birds’ weight.
From the stiff yet flexible central shaft spring fine filaments called barbs. Each barb has a central shaft fringed by smaller ribs called barbules. The barbules are equipped with tiny hooks that mesh with neighboring barbules and hold the feather together in a flat, smooth web.
Preening is the process by which birds keep their feathers clean. A bird begins this conditioning operation by rubbing its beak over an oil gland at the base of its tail. Using its beak as an applicator, the bird spreads the oil over a patch of feathers, and then runs them through its beak, nibbling as it goes. This process straightens rumpled barbs and zips their hooklets back into place besides removing dirt. Doing one area at a time, a bird preens its entire body, paying particular attention to the flight feathers.
Pigeons and herons are among the birds that lack oil glands. Instead of using oil, they preen with the fine powder produced by specialized powder-down feathers.
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