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
What Bird is That? author Nick Earls' 1999 young adult novel "48 Shades of Brown". The 48 shades refers to the number of distinct browns used by Cayley to describe bird plumage colours. What Bird is That? What Bird is That? A Guide to the Birds of Australia is a book first published in 1931 by Angus & Robertson in Sydney. Authored and illustrated by Neville William Cayley, it was Australia’s first fully illustrated national field guide to birds, a function it served alone for nearly 40 years. In 1960 it was rated the all-time best seller in Australian natural history. "What Bird Is