With three or four flashes I didn't get a same resoult.
Three flash on a bird and still dark and the background even darker with only one flash. If I photographing under better natural light conditions (or I would use higher ISO film), a ghost shadow appear around the wings. So if I want to freez the wings it needs least 1/17000 illumination time, and if I don't want the sahdows around the wings, I need a same flash duration on a background too, but also I have to photographing in a low natural light conditions so the fashes must be the main ligth source! Otherwise the shadows appear around a wings! I don't have as much manual controllable flashes as you have, so I tried once one of my non controllable flash on a background and already the shadow is appeared around the wings, because there was to much the different of the flash duration between on a bird and on a background.
Some of your photo seems to me was taken under natural lights and only the bird was illuminated by flash.
I can see only one shine spot in their eyes! When I did use two flashes there is two spot, if I did use three flash, three spot are wisible in the bird eyes!
I have two Nikon SB-800. At 1/32 power the duration is 1/17800. With Softbox I have to place the flashes so close, to the flowers, and the birds are affraid to fead on them. Without softbox, I can place them farther, but I got a lot of gray spot on the ruby trhoated hummingbirds! I read about, they need to be light with soft lights to get the colors.
But I know some photographers use only one or two flash to freez the wings and they photographing under a very good natural light conditions, so they not need flashes on a background, then they are clone out in Photoshop the shadows around the wings.
That's why I did ask you how did you get thees shots?
Under natural lights I got the colors, I got the background, but the wings are blurry or if I use one flash to freez the wings still some blurry shadow appear around them.