[A male Anna’s hummingbird perches on a small branch. He makes buzzing sounds. At first he appears all green. Then he turns his head, and it becomes bright red. He continues moving his head, which switches back and forth between red and green in color. He flicks his tongue several times, then flies away.] [Explore MacaulayLibrary.org]

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At first glance the male Anna’s Hummingbird (Calypte anna) is solidly green. Then with a twist of his head he reveals a flash of shiny red brilliance. This color show is made possible by the way the feather microstructure reflects light differently as the viewing angle changes. During his spectacular aerial courtship displays, he advertises this red badge to female spectators by orienting toward the sun. This colorful element of surprise is key to his mating success.