Many of you were probably fascinated by the segment of the
work showing that the Anna male courtship dive involves production of short tones by air flow over tail feathers. There's an article in this week's "Science" (by Elias, Clark and Prum; the latter's wife was the producer of the film) that takes the matter further. Here is the abstract:
"During courtship flights, males of some hummingbird species produce
diverse sounds with tailfeathers of varying shapes. We show that these sounds are produced by air flowing past a feather,causing it to aeroelastically flutter and generate flutter-induced sound. Scanning laser doppler vibrometery and high-speed video of individual feathers of different sizes and shapes in wind tunnel revealed multiple vibratory modes that produce a range of acoustic frequencies and harmonic structures. Neighboring feathers can be aerodynamically coupled and flutter either at the same frequency, resulting in sympathetic vibrations that increase loudness, or at different frequencies, resulting in audible interaction frequencies. Aeroelastic flutter is intrinsic to stiff airfoils such as feathers and thus explains tonal sounds that are common in bird flight"
There's also a piece in the NY Times: dotearth.blogs.nytimes.com/2011/09/08/a-hummingbirds-musical-tail/
The picture shows a trumpet creeper in full bloom.