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
This Bird Has Flown – A 40th Anniversary Tribute to the Beatles' Rubber Soul This Bird Has Flown – A 40th Anniversary Tribute to the Beatles' Rubber Soul This Bird Has Flown – A 40th Anniversary Tribute to the Beatles' Rubber Soul is a tribute album by a variety of artists that commemorates the 40th anniversary of the release of the Beatles' 1965 album "Rubber Soul". It was released on October 25, 2005 by Razor & Tie. It follows the track listing of the UK version of the album, although the two songs added to the American release are available as bonus tracks on iTunes Music Store. Writing for Allmusic, music critic Stephen Thomas