The trail into Boston Lot and to the lake begins from the more northern parking area along Route 10 across from the Wilder Dam.
There are a number of excellent birding spots along the trail to the lake, especially the powerline area and a small meadow on the left shortly before the lake.
Here is a group from early May, 2016 at Boston Lot Lake.
Here are photos of some of the species you might find at this great site.