01:35 am - Pearl Crescent (at Deerfield, MA)
Before he took me back to the train station in Fitchburg, I dragged Monty outside to look for birds and bugs with me. We found some ski slopes, which we climbed amid clouds of grasshoppers.
At the top, we found an excellent bird watching spot. We saw a number of as-yet unidentified sparrows, a towhee and a phoebe (all hunting insects in the grass). In the trees there seemed to be woodpeckers that we never got a good look at, and also a white-breasted nuthatch.
The little butterflies that seemed common high up I never got a sufficient picture of to identify, since I fumbled the camera settings. There were also bigger dark butterflies with a splash of orange at the underside tip of the forewing, which we saw (with binoculars) at the edges of the woods, sometimes perched vertically on tree trunks. I can't find an exact match, but the Common Wood-Nymph (Cercyonis pegala) seems possible.
On our way down, I did get close to a Pearl Crescent (Phyciodes tharos), shown here.
Butterflies often look much brighter and crisper on the wing; I played with the colors a little to try to bring out what I think I saw, but for reference, the original colors are here. (Decide for yourself whether I overdid it.) 
I do plan to try with a much smaller aperture next time this comes up; my default for small things is as big an aperture as I can get (which did do nicely at blurring a distracting blade of grass here) but the messy background problem always seems to be there for butterflies regardless.
Image editing...
Re: Image editing...
After a little research, I phoned the nice people at 2filter.com; they sold me a neutral density filter, with the explanation that a polarizer would distort the colors oddly. The ND filter is basically just a "make it darker" filter but it's supposed to do what I want, and if nothing else it will let me use my full aperture in bright daylight.
After I put down the phone, I regretted not getting a polarizer to play with but I couldn't think of a way to say "actually, I want to ignore your advice and buy both". 2filter has nice people, but you have to talk to someone to buy anything, because their web site bears no relation to what they have stocked or inventoried.