Confusion

I recently filed IFR and received a clearance from Ground. As part of the
clearance, I was told, "... after departure turn left heading 300 ..." I
taxied to the active, did my run-up, called Tower and said I was ready for
departure. I was soon cleared for takeoff.

At about 1000 AGL, I began the left turn to 3000.

About a minute later, when I hadn't yet been told to contact departure, I
asked Tower if they wanted me to contact departure. That's when the
confusion began. The controller said, "I didn't know you wanted to go to
departure, but, yeah, you can contact departure. Good day." "Well, I'm IFR,"
I replied. After a brief pause, Tower said, "Roger. Do me a favor, squawk
1200. I can't give you departure. You didn't tell me you were IFR. I didn't
get you a release."

I said I'd proceed on course VFR and asked if they'd get me a clearance.
They soon got it and handed me off to departure.

Guess I'll remember to remind Tower that I'm IFR from now on, although I
didn't think that was necessary. At least in this case, it was.

Jon