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 Creek (Wisconsin) with drumlins and scattered muck deposits. Soils are predominantly well drained silt over calcareous sandy loam till." The original vegetation cover is primarily white oak, black oak, bur oak, marsh and sedge meadow, wet prairie, and lowland shrubs. Calamus Creek is part of the larger Upper Rock River Basin. The of the streams comprising the Calamus Creek watershed cover , or 19315 acres, with 54.39 acres covered by five unnamed lakes and 3627.39 acres of wetlands. The watershed includes extensive wetlands, some of which are in the process of restoration. Parts of Calamus Creek are designated wadable nursery waters for