Pretty much every serious bird photographer has a big long heavy lens and it seems they use the same equipment. The most popular and de facto standard tripod head is the Wimberly Gimbal. The Markins M-10 ballhead is used as well.

For tripods, Gitzo is by far the most popular brand, with one model being the Gitzo 1340 Mk II. These are excellent 'legs', the best, but they are expensive, large, and not light.

Before I focused on birds and before I had a heavy lens, I bought a Sunpak 523P, a lightweight carbon-fiber tripod, perfect for hiking and travel. I never much liked the head, but I think it was more that I didn't like tripods. But I knew I needed one because I wanted to start shooting at 600mm. I read some good reviews about the Manfrotto 393, which is designed to hold very large lenses, and wondered if it would work with my Sunpak tripod legs. Although I used that combination for half a year, it isn't quite sturdy enough, and I recommend the Manfrotto 055XPROB Tripod or Manfrotto 190XPROB Tripod.

Romy Ocon, a well known Philippine bird photographer, uses the Manfrotto 393 and has written rave reviews. He writes he has all of the benefits of the Wimberly 'gimbal' design, but at a fraction of the price (about 1/3 actually). I agree. Some comments:

The Manfrotto 393 is very solidly constructed; it can be dropped on concrete with almost no worries.

With my lightweight tripod, swinging the head especially quickly will cause a second or two of wobble from the bending of the legs (assuming the tripod is fully extended). I presume this would be less noticable on a large Gitzo tripod.

The Manfroto 393 comes with a very long 'quick release plate'. This is the piece between the camera foot and the tripod. This gives you a lot of flexibility whe balancing your camera. I used the long plate to also attach my flash; keeping the flash on the camera with a long lens might cause the light to reflect off the lens or be blocked by the lens, and can cause something called the "steel eye" effect when photographing birds/animals.

For my lens, the best way to attach the flash to the tripod was with the larger metal square on the top bar facing towards me, and plate with the hole facing away from me. Then use the second small screw to attach the flash extension cord through the hole, after removing the plastic piece that keeps the screws from sliding off the quick release plate. Be very careful because as soon as you take off that plastic piece, your screws can fall off and are easy to loose. See photo to see what I am trying to explain. I bought a 'Canon off camera flash cable' retail for about $80, but check this link for better prices and third party manufacturers as well.

The 393 is easy to carry. One side of the square frame can be rested on the shoulder, while the other side is grabbed for support. I took me a while to get comfortable carrying it this way, and with the lens is still heavy, but eventually I was very comfortable placing the 393 on my shoulder.

Under the rubber cover for the horizontal rotator part is an adjustment screw hole. Romy wrote he needed to adjust this. I did not.

Always follow good tripod technique. Double check your tripod's stability every time you move it. It is easy to move from a hillside to a flat area and forget one leg is slightly extended. Always keep the legs extended as wide as possible. For stability, always extend the thicker parts first, and be aware that a tripod that is not fully extended is more stable that one that is not. Watch out that your tripod is not in a walking path.