February 20, 2008
Anna's Hummingbird Chirp Dispute Solved
The male Anna's hummingbird has a very entertaining courtship display, where it climbs maybe 100 feet and then dives down just short of a perched female. It breaks hard and its momentum causes it to climb again. At the bottom of its dive, it produces a loud chirp or squeak.
Last month, researchers at UC Berkeley published their determination that this sound made at the end of each courting dive is generated, not vocally, but mechanically, using the inside edge of the outer tail feathers.
Grad student Christopher Clark studied Anna's (Calypte anna) for three years before publishing in the 28 January 2008 Proceedings of the Royal Society B (Biology) that he and co-worker Teresa Feo had solved what was a minor controversy about how this buzz was generated. Clark and Feo, and many assistants over the years, lured male Anna's using stuffed females and a high speed camera to show how the males would snap open their tails at the bottom of a dive to coincide with the sound. They used a wind tunnel to determine whether, which, and how the feathers vibrated.
Almost 70 years ago, another grad student had recreated this sound by swinging an Anna's tailfeather through the air at the end of a bamboo pole. In 1979, the Curator for Birds at the California Academy of Science published an article declaring the sound to be a vocalization.
