BBC Life documentary always had an "On Location" at the end. Here are two examples.

One involves a lot of fake, they searched for a spot outside to observe and then rebuild the whole set indoor in order to be able to film growing of the plants [1].

In the other one they follow a dragon hunting a buffalo around for a long time trying best not to interfere [2].

But there is more, for one episode a cameramen built a shelter to hide himself from a bird. He had to improve it and stay for a long time to finally catch his footage. (Couldn't find it, sorry)

[1] http://www.youtube.com/watch?v=VrDnCLczYA4

[2] http://www.youtube.com/watch?v=D2-mTbv8gYo

One of the great things about the BBC natural history unit's programmes is that on the DVDs/Blu-Rays/Broadcasts they tend to show additional footage of how certain scenes were captured. They do tend to have the whole 6 weeks out in the middle of nowhere waiting for the perfect shot stuff going on, but of course that tends to be for one scene.

The other thing I've noticed the BBC do is they reuse footage from one documentary in another, which I guess is fair enough if it's good footage. I'd also be surprised if there wasn't some clever editing with audio to get the results.

I've always assumed that the sound effects from their underwater shots were studio effects.