It is difficult to be sure without clearer pictures, but my best guess would be a female (and/or immature) Brown-headed cowbird.
This is based on the heavy conical beak, my guess at the size, the overall grey-brown coloration, dark eye, dark beak, dark legs, and the faint suggestion of a line behind the eye. In addition, this is a common species in many parts of Massachusetts.
If you have seen these cowbirds (the males are quite distinctive) in your area that would support this idea.
Public domain image from USGS.