Half truths here. A duckling's uropygial gland starts to develop at 7 days, is generally fully functional at 14 day. The oil from the gland serves 2 main purposes....1 feather maintenance (why do humans use conditioner?), and there is the suggestion of an anti-bacterial component to help maintain feather integuity, additionall, in some birds, it will alter plumage appearance to other birds. It DOES not provide water rellency. Water relllency comes from the contact angle the feathers make with the water (Rijke, 1970. Ostrich Supplement 8:67-76). Scanning electron micrographs show that the overlapping of feather barbs and barbules creates a contact angle similar to the contact angle produced by Gor-Tex, which provides water rellency. The importance of maintaining feather quality is DIRECTLY related to maintaining feather water rellency. Take a look at: Stettenhelm, P.R. 2000. The integumentary morphology of modern birds: an overview. American Zoologist 40:461-477.
Clint
