Are they the ones I heard about nesting around Kiwanis Lake right in town in York?
That might explain the sighting although I'm 8ish miles above that, I'm pretty close to some other good habitat with the wide, shallow Conewago Creek and Pinchot Lake not far.

I'm a transplant from Schuylkill Co. 7yrs ago which could also explain why I have never seen one before this as well.