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 105.1 males. For every 100 females age 18 and over, there were 110.4 males. The median income for a household in the town was $50,000, and the median income for a family was $54,107. Males had a median income of $33,636 versus $24,671 for females. The per capita income for the town was $19,818. About 5.5% of families and 7.8% of the population were below the poverty line, including 13.0% of those under age 18 and 5.4% of those age 65 or over. Calamus, Wisconsin Calamus is a town in Dodge County, Wisconsin, United States. The population was 1,005 at