privatebydesign said:
There are much more powerful options than on camera style strobes. As Eldar says one of the first is the Profoto B1, and at 600Ws it is about 10 times more powerful than a 600 EX RT, and you can get focusing reflectors that can columate that power. Then there are comparable and more powerful options from Broncolor, and much cheaper and comparable models from Godox/Flashpoint, the AD600 can be doubled up to a single head to give you 1200Ws. If you don't mind taking an inverter style power pack people like Profoto make 1000Ws single heads that are HSS and ETTL capable.
As always it is a trade off between power, price and portability.
For instance the Profoto D2 and PCB Lithium Extreme are going to give you 20 flashes per second with full ETTL and HSS for around $2,500, expensive for one light but it has the capability of 14 600 EX RT's. Or the Godox/Flashpoint AD600 will give a more modest output and recycle for $600.
We get so wrapped up in camera advances we often completely miss the gigantic advances and options we have in lighting now my go to source for flash news is flashhavoc.
Scott, you beat me to it
I normally don´t use flashes for birding or wildlife. The reason is somewhere between ethics and laziness. However, I have lost enough shots, due to lack of light or, as in this case, subject is in dark shadow with bright backlight, to be willing to carry a bit more stuff around. From an ethics point of view, I must admit that I have yet to see any bird/animal react to the light, unless it is straight into their face.
For shots like the ones I took of the woodpecker, I find the 600 EX-RT too limited. Even with an external power pack, you don´t get more than 1 fps. Without the powerpack, you´ll get a lot less.
The Profoto B1 is a great package (actually B1X now). However, besides being quite pricy, it does some strange things. One is slowing down the max fps. I can understand that it slows it down to secure correct lighting for all shots. But, for reasons I do not know, it is slower in AF Servo mode than in One Shot.
Added comment: If you shoot in manual mode and One Shot, it will give you the full fps, as long as it is capable of recharge. In a situation like the one I was in, with app. 20 meters to the subject, it may give you a little less. I will try it out and report back. I can also use both B1 units, to give me more power.
It would be nice to have full flash availability at 14 fps and HSS, but I don´t see, with my limited use, that I would add a D2 package to my outfit. (My character is low though, so you never know ... :

)
I have read a lot of nice stuff about the Godox AD600, which appears to be great value for money. A friend of mine just ordered a pair. Will be interesting to see how they work in similar situations, even though, at up to 2.5s recharging cycle, it will not solve the high fps problem.