What makes plumage waterproof?

Abstract

It has been a common belief that the plumage of birds is water-repellent because the feathers are anointed with the secretion from the oil gland. A comprehensive survey of the literature in this field has been given by Elder (1954). When I observed that some changes in the diet caused a loss of the waterproofing of the plumage of young Tufted Ducks, I supposed that these diet changes in some way interfered with the functioning of the oil gland (Fabricius 1945). The disturbances easily occurred when the ducklings were fed on fish, but disappeared if they were fed on insects. The oil gland, preen gland or uropygial gland is the only skin gland in the birds, and it is known that the skin gland of mammals are dependent for their proper functioning on some vitamins of the B-group.