I wouldn' t call it unethical, but there are many times when it is inconsiderate to the other hunters in the woods and in my mind it is always dangerous with other hunters present. I have stalked turkeys that were a short distance away so that I could be reasonably sure there were no other hunters. I do not, however go after a bird when I know there is someone already in that area or the bird is a long ways away. If I hear hen calls, crow calls or owl hoots and I know it' s another hunter, I won' t go anywhere near that area.
I have been messed up by other hunters sooooo many times in this manner, that maybe I' m not a good one to ask.

Public lands are usually crawling with hunters. If you' re sitting in one section of woods and there is a bird gobbling in the next section of woods, the chances of that bird being over there with nobody working him is pretty much nil. There will almost always be someone there and if you try to stalk them, you are just going to mess up the other guy' s hunt as well as put both of you in a dangerous shooting situation. You shouldn' t even be asking yourself " Can I stalk these birds?" The better question would be " Am I going to get a load of number 4' s in my face when I stick it over those bushes?"
The other thing I would mention (and this is my pet peeve) is that after a week of guys jumping up and running to every bird that gobbles, you can pretty well forget hearing much gobbling. Public land birds are far warier than private land birds and all it takes is one time bumping them and you sometimes won' t hear that one gobble again. You make a sound on a call, and they go the other way. In short, some of them become unhuntable.
You will have much more luck on public lands being in the right place before daylight and sneaking back out if the birds don' t show. It is far safer and the birds will remain huntable for the next time you come back.