The down has its fine quill and a stem bearing the close down which in water fowls keeps the warmth of the body at an even temperature whether in or out of the water. It would be an error to suppose that the feathers grow in the skin without any order, simply close together. They are in point of fact divided into areas between which the flesh is generally covered with down, and all is arranged in a system of grouping which, the feathers being rightly placed over one and another, does not in any way interfere with the movements of the body, each movement being in perfect conformity with this feather covering. The feathered areas can be moved independently with the aid of the muscles, and this renders the cleansing of the individual feathers easy and the removing of the fatty substance, which is a matter of great importance. If we watch we see that the bird moves the feathers separately in this cleansing process, drawing them through its beak, and so removing any bits of fat and oily substances that may have collected about the fat glands.
View of the back of the bird, showing the feather tracts.
The spaces between the tracts are covered with down.
USEFUL.