as fast a 400-500 or so prime you can afford is a better bet
Judging by the link he's posted above the view is looking down.
Its always worth putting in a bit of fieldcraft too. You might find they are closer when they first get going in the morning, or last thing at night. The wildlife photography the general rule is that you get putting more time in is a shorter route to success than more money. Or as Shaw put it 'to become a better nature photographer, become a better naturalist'.
At the end of the day are you going to do any more than upload them to flickr?
I'm sure I've already written all of this on the other thread.
The main issue is the effect on AF. I'm not convinced any AF will perform with an effective f8 lens. And with your whizzo camera, you can do what the fuck you like with the files except post-focus.
There seems to be mixed messages about the tape trick, some stating it works fine others say it stutters
Sigma 100-300 f/4 + 1.4x - interesting combo this. I can trade the 70-200 and basically only pay for the TCon,
A crop body is a daft idea - just crop the 5D file and get a better file with more pixels
What Dave said about trading the 70-200 for a 100-300. Unless you've got other issues with the 70-200? A 400/5.6 is a great lens, ideal entry lens for wildlife photography. If you find one, I'd hang on to it.
A 5dii fileat 200mm cropped to 400mm eqiv leaves you with what, about 5mp? Pretty sure even an old 10mp crop sensor cropped to 400 mm equiv would beat that.