That's not good to hear as you are the third different location I know of where activity is way down this year (me in Germantown, parents in northern Calvert, and you). I've kept notes for over 10 years and it's been very consistent: arrive late April, lots around except for a bit of a quiet period in mid-late May(probably nesting), then lots again for rest of summer. I keep two feeders out of sight from each other plus lots of attracting flowers. Other years I could sit by a window or on the deck and see them around almost all the time. Now I might see one brief visit if I sit out there for a half hour.
I've had whole days where I didn't see a single one and that never happened in past summers. I was wondering if the dryness or the super-warm winter had something to do with it but that doesn't make sense. I hope there hasn't been some kind of big population decline like what has happened to monarch butterflies some years. I have not been able to find anything doing web searches.
It's still just early June so I hope they show up soon.