Final answer:
The feather covering on birds is called plumage, which includes contour feathers for flight and down feathers for insulation. The more drab down feathers in young birds provide camouflage and warmth.
Step-by-step explanation:
The feather covering on birds is known as plumage. Young birds often have more drab versions of this plumage which serves as camouflage. In adult birds, plumage includes contour feathers and down feathers. Contour feathers give birds their streamlined shape and flight capabilities, helping reduce air resistance. On the other hand, down feathers are specialized for insulation; they trap air next to the bird's skin, keeping the birds warm. Down feathers' structure is loose, with barbs that do not interlock tightly, which helps trap the warm air. Newly hatched birds are covered almost entirely in down, providing them with a warm coat that establishes a thermal boundary layer, protecting them from the cold environment.
The feather covering on birds is called plumage. Birds have two main types of feathers: contour feathers and down feathers. Contour feathers have parallel barbs that branch from a central shaft, forming a strong and flexible surface. Down feathers, on the other hand, have loose and fluffy barbules that trap air for insulation. When birds are young, their plumage may appear more drab to camouflage them.