Powder down
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208060638
2008-04-25T07:13:27Z
Jmorrey
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{{Unreferenced|date=April 2007}}
'''Powder down''' is a special type of [[down feather]]s. They occur in a few groups of apparently unrelated birds and thus are probably [[evolution]]ary [[homoplasies]]. These down feathers differ from the usual down as they are exceptionally fine and produce a dust between the frons. The bird takes this dust from its powder down feathers and coats all its external feathers with the dust. This dust mainly provides the bird with some waterproofing for the main flight feathers so it can still fly in the rain. It also conditions the feathers and keeps the [[barb (feather)|barb]]s of the flight feathers interlocked to provide good lift. It may also be useful in suffocating [[feather louse|feather lice]] and other [[ectoparasite]]s by clogging their [[Invertebrate trachea|tracheae]].
Powder down is found in birds such as [[heron]]s or the [[Kagu]]. Larger species of white [[cockatoos]] (such as [[Sulphur-crested Cockatoo]]) also have powder down, located on their flanks (sides of the body).
Powder down feathers are probably seen most easily in the [[cockatiel]]. In this popular cage bird, they are located at the lower back beneath the outer tail feathers' bases. Cockatiel powder down is by far the softest down in living birds{{Fact|date=March 2007}}; the powder down feathers, when used up, are pulled out by the bird allowing new ones to grow. They are like a fluffy ball and when rubbed between the fingers the powder from the down will cover the fingertips.
Birds with powder down usually have a reduced [[uropygial gland]], but not all birds with vestigial or missing uropygial glands possess powder down.
==External links==
*[http://www.britannica.com/eb/topic-473187/powder-down Encyclopedia Brittanica online ''powder down (feather)'']
[[Category:feathers]]
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