. Principles of economic zoo?logy. Zoology, Economic. 262 BRANCH CHORDATA first, second, or even the third spring the plumage becomes like that of the adult. The time of molting varies not only among different species, but often among different individuals of the same species, ac- cording to sex, age, and physical conditions. All birds molt after the nesting season. Some birds lose a few of the body feathers in the next spring before the nesting season, while many lose the body feathers, but not those of the wing and tail. Some change. Fig. 213.—Pterylae and apteria of Gallus bankiva (Nitzsch)
. Principles of economic zoo?logy. Zoology, Economic. 262 BRANCH CHORDATA first, second, or even the third spring the plumage becomes like that of the adult. The time of molting varies not only among different species, but often among different individuals of the same species, ac- cording to sex, age, and physical conditions. All birds molt after the nesting season. Some birds lose a few of the body feathers in the next spring before the nesting season, while many lose the body feathers, but not those of the wing and tail. Some change. Fig. 213.—Pterylae and apteria of Gallus bankiva (Nitzsch): a, side; b, dorsal side. Ventral color by wearing off the fringes of the feather tips, and others at this season are adorned with special nuptial plumes,' such as the aigrette of the heron, for which these birds have been so slaughtered. There are no periodic molts of the skin, as in reptiles, but the horny layer of the integument undergoes a constant renewal, as in mammals. Some penguins, it is said, "exhibit the old rep- 1 Chapman, " Bird Life," p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Daugherty, Lewis Sylvester, 1857-; Daugherty, L. S. , Mrs. , 1859-. Philadelphia, London, W. B. Saunders
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