I hate to say it, but I have a feeling this guy's co-workers may put an end to the whistling before you make any headway. Then you'll have a different problem on your hands -- disciplining because of workplace violence!

Jerks at work are a fact of life. Maybe he will get bored with his stupid routine. Like mom said, don't give him the satisfaction of responding and maybe he'll stop. Easier said than done I know.

I can understand this problem so very well! Our HR head whistles in his office and it carries throughout several other departments. Also, we have a woman in my department that hums, sings, whistles and what-not quite frequently. Two fortunate things save my sanity though - 1. HR guy is not in the office very much these days. 2. My department gets along well enough that we can point out what our co-worker is doing and she will laugh then stop - many times she doesn't realize she is doing it.

My advice - go to HR and explain what is going on and the steps taken to that point. They can then document everything and would hopefully offer advice or to speak with him themselves. Good luck!!