Feather These barbules have minute hooks called barbicels for cross-attachment. Down feathers are fluffy because they lack barbicels, so the barbules float free of each other, allowing the down to trap air and provide excellent thermal insulation. At the base of the feather, the rachis expands to form the hollow tubular "calamus" (or quill) which inserts into a follicle in the skin. The basal part of the calamus is without vanes. This part is embedded within the skin follicle and has an opening at the base (proximal umbilicus) and a small opening on the side (distal umbilicus). Hatchling birds of some
Calamus, Wisconsin Calamus, Wisconsin Calamus is a town in Dodge County, Wisconsin, United States. The population was 1,005 at the 2000 census. The unincorporated community of South Beaver Dam is located in the town. The unincorporated community of Lost Lake is also located partially in the town. The town was founded on January 22, 1846. According to the United States Census Bureau, the town has a total area of 36.5 square miles (94.7 km²), of which, 36.1 square miles (93.4 km²) of it is land and 0.5 square miles (1.2 km²) of it (1.29%) is water. As of the census of 2000,