Mrs. H - the certified birder (I am
not making this up!) - is sitting at her 'pute with five different birding books on her lap (including an owl book). It is
still really hard to tell whether it's a great horned owl or a long-eared owl. Behavior is odd for the latter (they're usually up close to tree trunks in the daytime and virtually invisible)... face and other aspects of the coloration, however, resemble the latter more than the former (although the 'ears' appear to be wider-set than they should be on the latter). Both species are found in your area
The latter is about 15", so if it really is smaller than a great horned owl (size 17 - 22" or so), then perhaps it is a long-eared owl.
Mrs. H volunteers at a Mass Audubon site; she'll check with the pros on her volunteer day next week!