Brother Calvin,
It is a tough choice. (everything in life is about tough choices lol). You should know my stand on this. (see my sig lol) I was once exactly in your shoes, and asking the exact same question. I was advised some time ago by one experienced nature photographer to get the lens first. Body later. I did the exact opposite and now have really mixed feelings about my choice.
First off, lets consider the benefits of either one. A pro body is truly a wonderful thing coz it has the AF speed, buffer and fps which allows you to capture the shots more easily. In wildlife and nature photography, speed is the key as crucial moments can happen very quickly. The main factor is AF speed (i.e. the time it takes for cam to lock onto the subject). Yes lens does play a part too, but usually the body is the main culprit here. With non pro bodies, focusing tends to be slower and takes longer to lock on (i.e. it hunts). It can be extremely frustrating sometimes, the bird could be merrily displaying in front of you but your focus is hunting all over the shop! By the time it locks the bugger has already disappeared.
Now the lens. A long telephoto lens is truly the most important tool in any serious wildlife photographers's bag. Why? It offers superb image quality and most importantly,
reach. Which negates the need to stack teleconverters and also maintain a safe working distance from the subject. It takes some time to master yes, but with the proper hands it can produce excellent results with just any body, no matter 1 series or your 350D.
Here's my suggestion. You might possibly consider this path which is more cost effective than just upgrading both lens + body to your desired combo which will be a killer to your bank account. Sell off your 350D, perhaps a couple of other gears you feel you do not use that much, maybe even your 100-400L, and put the money on a 2nd hand 20D or 30D. The AF is better than the one on 350D, more robust body, and also 5 fps, with this body it is a very decent combo for bird photography. You also keep the 1.6x crop factor for added reach. Then, go for the 300mm f2.8 or 500mm f4. The pro body can wait till later, as prices are falling all the time, but at least for the time being you will have a decent working combo in your hands.
you are right though. eventually you will end up with 1dm2 + 500mm :bsmilie:
This is almost a given. Most bird photographers I know who end up in this money and time sucking hobby end up with this combo. This poison has no known cure. :bsmilie:
