I know from experience that prey animals in particular have a well developed sense of smell used to detect danger. Many times i have been watching deer or other mammals and felt a waft of breeze on my neck and seen heads shoot up obviously smelling me.
But what about birds ? I know they have fantastic sight and if they couldnt hear they wouldnt call.
What I am thinking is just how much is my smell going to put off birds approaching when for instance I am sitting in a hide and indeed is there any smell I could use that would attract rather than repel birds ?
So birds can smell some better than others and some at least use smell when feeding but that doesnt answer my question of how much if any would the smell of my sweaty body effect my chances of seeing that bird of a lifetime.
As a smoker I have often wondered about this myself, although when birding I rarely, if ever smoke, but the smell must still be there On the odd occasion when being alone I may have had a puff or two. In saying this I have never noticed any difference in bird behaviour, although smoke as an un-natural smell to them may not be deemed as any threat. On a slightly different note, I do also employ a different tactic which I picked up as a stalking carp fisherman back in the UK many years ago, whereas I never stare or make eye contact with the bird (or fish), I have found this to work with positive results , when looking away, squinting or wearing dark glasses the bird (or fish) appears much more relaxed in my presence