by Dick Woodward » Fri Mar 04, 2016 5:55 pm
There is no reason why you cannot politely inform the prof that you have to make a decision by April, and, that while you would really like to join his lab, you have to make a decision in a fixed time frame - could he therefore let you know what the status is.
My daughter had the same issue (in a different field). She sent that sort of e-mail - "you're my first choice, but I have another offer" - and immediately heard back with an offer.
In my opinion, if the prof is annoyed that you asked this question, this is not a place that you want to work. The prof will have basically demonstrated that he has no concern for his postdocs, and I don't think that it will be a happy experience working there.
I had the mirror image of your situation when I moved into industry. The company that I felt that I wanted to join made me the first offer - before I had even interviewed with the other two. I called the hiring manager and said "I think that I want to work with you, but I owe it to myself to go on the other two interviews so that I am certain." (The interviews were all within a week or two.) His comment was something to the effect of "Go ahead - I want you to be certain that this is the place for you so that you will be happy and productive." By the way, it was a great place to work.
Best of luck.
Dick