Apparently, that seat is in the middle of one of my boxwoods.
Today I finally started pruning the boxwoods. It's one of the projects that, once started, so clearly is way overdue that I wonder my fellow gardeners had not long since taken me aside for an intervention.
At any rate, as I clipped merrily along, I spotted a nest. I came back with my camera, assuming it was empty, but no! Two little blue eggs, and once I withdrew, the catbird couple flew around to see what havoc I had wrought.
I dearly hope I haven't scared them away. I think I can spy on them from my bedroom window if I stay quiet as a mouse.