Scientists at Yale University discovered males produce the loud sounds as the air flows past the tail feathers in the dive, causing them to flutter, a National Science Foundation release said Thursday.
When the courting male bird reaches the lowest point of his dive, which can begin anywhere from 5 to 40 yards above a perched female, he rapidly spreads and then closes his tail feathers, causing them to flutter and generate sound.
Yale researcher Christopher Clark says males of different hummingbird species all have their own signature sound. The size, shape, mass and stiffness of the hummingbird's feathers create the tone of each species' particular sound, he said.
"The sounds that hummingbird feathers can make are more varied than I expected," Clark said.