<unk>  variations<unk> s are epidermal growths that form a distinctive outer covering, or plumage, on dinosaurs, both avian (bird) and some non-avian (non-bird) and possibly other archosauromorphs. They are considered the most complex integumentary structures found in vertebrates and a premier example of a complex evolutionary novelty. They are among the characteristics that distinguish the extant birds from other living groups. Although<unk> s cover most of the bird's body, they arise only from certain well-defined tracts on the skin. They aid in flight, thermal insulation, and waterproofing. In addition, coloration helps in communication and protection. Plumology (or plumage science) is the name for the science that is associated with the study of<unk> s.<unk> s have a number of utilitarian, cultural, and religious uses.<unk> s are both soft and excellent at trapping heat; thus, they are sometimes used in high-class bedding, especially pillows, blankets, and mattresses. They are also used as filling for winter clothing and outdoor bedding, such as quilted coats and sleeping bags. Goose and eider down have great loft, the ability to expand from a compressed, stored state to trap large amounts of compartmentalized, insulating air.<unk> s of large birds (most often geese) have been and are used to make quill pens. Historically, the hunting of birds for decorative and ornamental<unk> s has endangered some species and helped to contribute to the extinction of others. Today,<unk> s used in fashion and in military headdresses and clothes are obtained as a waste product of poultry farming, including chickens, geese, turkeys, pheasants, and ostriches. These<unk> s are dyed and manipulated to enhance their appearance, as poultry<unk> s are naturally often dull in appearance compared to the<unk> s of wild birds.
Feather
Hives
Wart
Hoople 
Hair
Litter 
Guts UK
Hairball