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Chrysolampis mosquitus, 8-9 cm

Ruby Topaz Photograph by Luis A. Mazariegos A male in Colombia's Cauca River Valley shows off two dazzling aspects of hummingbirds: hovering and iridescence. The first arises from the most powerful muscles per unit mass of any vertebrate. The second results from microscopic, air-filled platelets in the feathers that act as prisms. Such dazzling plumage occurs mainly among male hummingbirds. Females, tasked with rearing the young alone, rely on duller colors to blend into the woods when nesting.