Lorant, Thanks for your comments. The flash is flash as main light not fill flash.... The BKGr is a print of light blue. (I do prefer somewhat mottled BKGRs but Linda likes the plainer ones as she often uses flowers in the set-up.) In this case the BKGR is supposed to represent sky. And unlike most of the folks who commented here I rather like it.
We traveled to Panama with three eight flash set-ups. 30 flashes, more than 30 light stands, background mounts, several hundred AA batteries, about 40 BKGRs, and a ton of other stuff in six extra pieces of luggage. You gotta love that....
ps: You can learn all the details of high speed flash hummer photography in Linda's great guide here:
https://store.birdsasart.com/shop/ca....aspx?catid=33