Feather development grows, its spathe, which is where the rachis and vanes attach, continues to form. When spathe is finished developing, the calamus begins to form within the base of the spathe. The calamus is the quill of the feather, which is the bottom portion that stays mainly within the pulp cavity. From there, the feather is fully developed and will remain as such until molting occurs, causing it to fall off. Feathers fall off during molting, which occurs in the at different times through the year depending on the type of bird. Birds can molt for seasonal, reproductive and many other
What Bird is That? 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 That?" was originally published in octavo format (239 x 158 mm), containing 340 pages bound in green buckram, with a dust jacket illustrated with a painting of a laughing