Seen last week near Scarborough Marsh, MA. Good habitat for Saltmarsh or Nelson's, both of which were sighted there that day, but doesn't look to me like either. Lacks the well-defined mustache of Savannah; and relatively fine streaks and white median crown-stripe should rule out Song Sparrow. Is it a possible Vesper even though not the perfect habitat?? Or a juvenile something?? Thanks for any help.
Do you have other photos of this bird? My first reaction was Savannah also, and I still think that's what it is, but there are features (white eye ring, apparent white outer tail feathers) that suggest Vesper.
Thank you all for looking. Chris: here is the only other shot I got of him, rather cluttered but does show the side of the face a bit better. Doesn't show the tail feathers well. It does seem to show the white band below the eye wrapping partially around behind the cheek, and an almost complete eye ring; and lacks any strong mustache, which made it appear somewhat like Sibley's description of a Vesper.