Yes. I know there are ball-heads that have been lately developed that are pretty good. And I also know that many of the newer version of lenses (both Canon and Nikon -- specifically the FL line of lenses) are light enough to be handheld.
BUT (and that's a big, very valid BUT) ball-heads won't give you perfect results in all conditions. And even with the newer lenses...hand-holding will lead to fatigue after some time. Besides, its almost impossible to properly compose your bird photographs when you are more "bothered" about holding up the lens...so again, we come back to the same point -- a sturdy tripod + a dependable gimbal head.
Gimbal heads at their very simplest are made of two L shaped hunks of metal (or carbon fibre) fixed to each other.
The Gimbal is fixed onto the tripod by means of a thread arrangement at the end of the horizontal arm of the lower L.
Another (slightly smaller) L shaped hunk of metal (or carbon fibre) is fixed at the other (vertical) end of the lower L.
This L has a Arca-Swiss quick release arrangement...and your long lens fits into this by means of a lens plate (that you fix onto your lens's foot.)
There are two soft twist knobs on the Gimbal head...tightening and loosening them gives you various degrees of "tension"for horizontal and vertical movement of the lens.
For instance, when you completely tighten the lower soft twist knob, the lower L arm of the Gimbal is now totally locked into place. This means you can't swivel the lens horizontally at all. Similarly when you completely tighten the upper twist knob, again the upper L arm of the Gimbal is now totally locked into place. So immaterial of an angle of 45% or 60% or even 90% you have a lens that is positioned rock steady!
As you can visualize, nothing beats the versatility of mounting a long lens on a Gimbal head. Especially when it comes to Birds in Flight...and when it comes to tracking flying waterbirds. In fact, if you want to get "set up" for a day of photography, there is no other way that is as "professional".
I use a Lensmaster RH-2 Gimbal head.


And, I must say I am very very happy with its performance so far.
I would definitely recommend the Lensmaster RH-2 to you if you are looking for a simple, no frills and solidly built Gimbal head.
Another very good Gimbal head is the Nest Gimbal head.
(No, I haven't used it yet.)
Naturally (of course) there are plenty of other Gimbals out there as well...Wimberly, Jobu Design, Really Right Stuff, etc, etc...and its all a question of how much you are willing to "blow".
Personally speaking, I am very very happy with the Lensmaster RH-2 and I think it does a great job!
A word of caution here though. While not very heavy -- and averaging around 1.5 kilos, Gimbal heads end up adding to your total laden weight. And there will be terrain in which you simply can't move with a lens mounted onto a Gimbal and tripod...where you have no option but to handhold it (or shoulder hoist it) and move on...
As such, I would say, do spend some time out in the field handholding your lens. It will come in "handy" for you down to line, Gimbal head or no Gimbal head!
