wunder · LibraryCHAPTER XIII.. Secondary Sexual Characters of Birds.
Read in the Wunder reader — freeSECONDARY SEXUAL CHARACTERS OF BIRDS. Sexual differences—Law of battle—Special weapons—Vocal organs—Instrumental music—Love-antics and dances—Decorations, permanent and seasonal—Double and single annual moults—Display of ornaments by the males.
The Descent of Man, and Selection in Relation to Sex · The Wunder Library — complete classics, free to read, with narration.
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