Down feathers lack hooks so they will fluff out for insulation. Duck flight feather magnified at same rate as 1 cm ruler. Dark line through center is feather's shaft. Barbs branch off from the shaft. Duck feather at greater magnification with 1 mm for scale.
Barbs show up here with their smaller branches, called barbules.
Higher magnification with 1 ruler line for scale. Small hooks, called barbicels, can be seen on feather's barbules. Feathers can provide insulation, a water resistant body covering, ridgid surfaces for flight, even the sense of touch, all with minimum weight. Part of the Kaytee Company's site is a page on different types of feathers . An exhibit at the Smithsonian Institution tells the story of how the sale of bird feathers for women's hats jump-started the conservation movement in the United States.