The noise is produced by the wings as air rushes through them on his downward plunge.

BN

Rufus/Allan's create a sort'a metallic sound with their wings, unlike an Anna's which creates a lower frequency drone sound.

He's at it again this morning and it seems to be three notes , with the last trailing off . It's very loud and begins at about half thru this desent at me and ends as he sweeps past. I have trouble excepting it comes from his wings , for some reason . It seems more vocal

Yep -- feathers it is. Usually the outermost wing feathers. The closely related Broad-tailed Hummingbird (male) makes a very distinct wing trill because of the very sharp shape of the last wing feather -- quite different from other NA hummers. When this species molts that feather over the winter, it just "hums" normally until a new one grows in.

During a courtship dive, Anna's Hummingbirds can make a screech or popping sound near the terminus. This is apparently caused by the tail feathers... Weird, 'eh? And fascinating, too!

Here is a link that might be useful: Hummer Wing Trills

thank you , one and all . nice site