Feathers 25 
by true feathers, which overlap, protecting the body from 
heat and cold, dust and rain. 
Fic. 12b.—Last stages in the formation of a down feather, showing the plumes 
well above the surface of the skin, as in a newly hatched chick. All greatly 
enlarged. 
At the time of the first moult, this succession of 
feathers can be observed in almost any young bird, being 
more noticeable in large species, which have very thick 
