Found with others in High Pines area of Duxbury Beach (MA) 8:45am Aug. 27, 2009.
Other photos taken of these birds are in gallery "Prairie Warblers Aug 2009" under my "Umbrella Gallery"

After reviewing the extensive descriptive info in the Peterson Warblers Field Guide, I'm comfortable saying this is an immature bird (Pg 80: "Narrow, split whitish eye ring separates all fall immatures from adults"). I'm a bit stumped as to gender of this one because the grayness of the cheeks (auriculars) suggests the female, but the boldness of the striping on this individual suggests a male. Others in photos had less bold striping and almost certainly are females. The photos also show two underside tail shots that correlate nicely with the picture on page 105 in Peterson.

Personal note: the book doesn't emphasize how obvious and solid the gray auriculars were on these birds (check other pix) and evident the coloration was in the field.