(pending confirmation)
While watching 2 panicky not-yet-fledged Killdeer scurrying to avoid a pair of aggressively territorial adult Willets, I saw a sparrow drop into the nearby grass and for once the bird did not immediately scurry out of sight. I assumed it was a Saltmarsh Sparrow and, figuring (correctly) that I only had few seconds before it would disappear, I started clicking off photos. While these pix suggest Nelson's the experts advise that this is a juvenile Saltmarsh. The bird bird was quiet the whole time.

The bird was seen and photographed from the car between 8:33-8:35am just west of the first bend in the Gurnet-Saquish road after you come down off the Gurnet (approx. 42.005341, -70.604984). The skies were spritzy under dark low clouds, the wind was nil, and the temp about 67.

Photos taken with 400mm zoom lens and cropped to the subject before posting