【英语时差8，16】尾巴吱吱叫

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Ya?l: Nice tune Don, but can you whistle with your tail like an Anna's hummingbird²?

D: Hummingbirds³ can whistle with their tails?

Y: Male Anna's hummingbirds, which live along the west coast of North America, can! Scientists in California discovered this when they were studying the birds' courtship behavior. They noticed that certain high-pitched chirps⁵ were produced only when males made rapid swooping⁶ courtship dives. The chirps were produced at the bottom of the dive when the birds flick⁷ open their tail feathers.

One of the scientists discovered that the two outermost⁸ feathers of the male hummingbird's tails had an unusual shape. He plucked these two strange feathers from one male and then let him go in front of a decoy female.

The plucked male saw the stuffed female and started a courtship display to impress her. He swooped⁹ into the dive in front of her, but this time there was no chirp⁴!

The curious scientist then attached one of the tail feathers to a long stick and found that if he spun¹⁰ it around fast enough, the feather started to hum.

By holding feathers in a wind-tunnel, he found that at wind speeds of forty-four miles per hour the modified tail feathers make high-pitched chirps like the ones heard during the flight displays.

D: Wow! So the tail feathers work like whistles?

Y: Actually, it's more like a clarinet. When you whistle, the tone is produced by air whistling through a constriction¹¹. The tail chirp is produced by vibration¹² of the feathers themselves, like the reeds in clarinet mouthpieces.

D: Neat! Maybe they should change the name from "Anna's hummingbird" to "Benny Goodman's hummingbird"Y: Oh, Don...!  

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