Hello, isn't this forum amazing on how open people can be? I love it!
Here is my 2 quick cents. I JUST got into bird photography after focusing on mammals at zoos for a few years. I started with a 40D and absolutely LOVED that camera for birds and animals, just wished the high iso performance was better, but for a first camera i still love it. It can be had for around $300 used right now. When i went to upgrade that, i was hoping for a 7D but because of the japanese tsunami, it was impossible to find so i settled for the more expensive 5D II. 5D II is just bad for birding. Don't get me wrong, you could survive with it, but only having 9 tiny autofocus points is really difficult. So between the 5D II/III and 7D, the 7D wins hands down. When cropping a 5D II/III image to the 7D size, the image quality COULD be close or favoring the 5D, but the autofocus just destroys the 5D II (not the III).
And as for the lens, i started out with the 75-300mm which cost me around $150 new. It is technically a bad lens but it was great to learn how to use a long lens and figure out it's limitations. I next went to the 100-400mm and love love love it. It takes a little while to get used to, and the weight is noticeable but if you are serious about animal/bird photography it is a great lens. I personally love zoo animal photography and wildlife, but it's so hard to find mammals in the wild where i live, so i am focusing on birds since they are EVERYWHERE. I am now looking at getting the 400mm f5.6 fixed lens JUST for birding, or the 300mm f4 and started a few threads on this topic.
So to sum it up, if you are trying to save money/start slowly, you can do a 40D or 50D, or go all in with the 7D. If you get one of those you could buy the 75-300mm and play around with that until you can afford your next lens.
And lastly, i use a 1D III for my birding over my 5D II because of the large central autofocus point of the 1D III and the fps. the 1.3 crop is not the best, along with the 10 megapixels but i am happy for now with the combo, especially on sunny days i can use the 1.4x III extender.
Hope this helps!
1D III - 1D II - 5D II - 50D - 40D - EOS M.
16-35mm, 24-105mm, 100-400mm, 40mm 2.8, 50mm 1.4, 85mm 1.8, 135mm 2.0 . 1.4x III, 2x III. 270ex, 270exII, 430ex, 600ex