I can also definitely recommend a carbon fibre option because of the weight saving. A test I saw somewhere but can't recall also said that CF was less likely to vibrate than aluminium.
I also use my tripod as a monopod - just extend 1 leg and a quick strap of the 3 legs together high up with a bit of velcro 'onewrap' (brilliant stuff but try to get Velcro as some clone stuff is not so good)
I also prefer a ball joint / trigger grip as by the time I'd worked out which handles to twiddle on the pan and tilt head the picture was often lost. Get the best ball had you can afford as the friction control is so much better than on cheap heads (I wasted money on 2 cheap heads before I learnt that lesson. For monopod use I would recommend the Manfrotto 234RC or similar as when using a ball head on a monopod, if its loose enough to track up and down, it is also loose enough to flop side to side, especially with a big telephoto / zoom.
If you expecting to track birds/ planes at any elevation (say 45deg from horizontal) make sure the mono/tripod extends higher than your eye line. Otherwise you will need to crouch to see the viewfinder (not at all comfortable.) for a monopod I invariably extend to maximum and place the foot well in front of me. I can then 'go high' with the camera very quickly by just pulling in the leg. Effectively the long leg becomes an near instant height adjustment. Place your feet open and at 4 o'clock and 10 o'clock, lean a bit into the monopod and you and the monopod are effectively forming a tripod. Looks a bit 'posy' but who cares if you get that perfect image.
Don't forget to disable optical stabilization when on a mono/tripod. When a lens is stable OS can apparently have the opposite effect! Do sometest shots for shutter speed - important for birds and prop aircraft in flight depending on whether you want wing/ prop blurring to show movement or be frozen.
For birds/ planes in flight use multi exposure. With luck one in 10 will be sharp and include the whole bird (thank goodness for digital.) I would also suggest manual setting if tracking birds in flight as if it flies across sky then trees then a building say, the exposure will inevitably be wrong - ussually on the best one of the lot. I recently read that take an exposure of the sky and increas by 1 and 2/3 stops for a dark/ black bird and reduce similarly if white /light as a starting point. Bit of experimentation required. Doing this may 'spoil' the sky but the birds will be correctly exposed. Use RAW if you can as it gives more latitude to mess round with exposure in post than jpeg ever can.
Now if only those birds would hover on command I'd get some good pics