Since so many of the participants are photographers, I'd like to add my own list of do's and don'ts for them. This list does not list the obvious points of ethical photography, though those must be followed too...it deals with how people should do photography while in a group.
Do not stray away from the group in pursuit of the photograph. Group leaders often find it hard to trace errant members, and even in scrub jungle, which looks tame and domesticated, it is easy to get lost, particulary on cloudy days when the cardinal directions are not clear.
If you find something interesting, do (quietly) let the others (or at least your neighbours) know about it. Clicking away in silence while others wonder what you have in your viewfinder...is not A Good Thing
When you find something interesting, and step up to take your photograph, remember to check if you are getting in anyone else's way. Many people wind up taking photographs of the backs of eager beavers who have stepped into the frame, intent on their own photography.
If you have a good zoom on your camera, do allow others to go closer.
Do not, in your eagerness to get closer, chase the subject away, so that others in the group get neither a good look nor a photograph.
Remember that others with smaller cameras and lenses, and mobile cameras too, are as much photographers as the ones with the bazooka lenses.
Silence your camera shutter sound. It's very impressive to hear the machine-gun sounds of a burst of shots, but it can chase away an alert animal or bird. It can also spoil someone else's video.
Do not keep interrupting the walk to show others your shots from this, or other, walks. Chimping (the process of looking at one's shots) can be done after the walk (or by yourself, if you want to check on something.). Showing other people your shots is fine if they have, for some other reason, missed seeing the subject, and want to see it.
Do take some shots yourself, and as fast as you can, allow others to get to your particular point, so that they, too, can take their images.
I once heard someone say, "I am glad I got the shot, and I am even more glad no one else got it." If this is your point of view, then nature walks in groups are not for you. To get unique shots, go by yourself. You may get those shots, but I assure you, you will miss out on the camaraderie, the multiple opportunities, and the safety benefits that group walks have to offer.