The Beaver Brook Duck Ponds in Belmont are one of the oldest conservation areas in Massachusetts. First established in 1893, the two ponds and associated trails have some pretty good birding. See the DCR for more. The ponds are on Mill St. and parking is just beyond the house mentioned.
The basic setup is two ponds, connected by a stream. There is a waterfall beyond the ponds and the stream continues out towards Trapelo Rd. Ducks (mostly mallards and mutts) are always present on the water, but there’s often other stuff as well. Wood Duck are regular as are Hooded Merganser in season. I’ve had Green-winged Teal several times. The right pond often dries out in summer, leaving moderate shorebird habitat.
My usual route is to start at the parking area and check the Duck Pond (the left one, the other one is the Mill Pond). There’s a trail to the left that runs into the woods and down along the waterfall that I’ll take if I have time. It can get a bit wet down at the bottom, where you cross a couple bridges and end up on the other side of the stream. Follow back to the right and uphill to get to the other side of the pond (or just go around the edge of the pond and don’t take those trails at all, just watch for overgrown poison ivy). Work along the back of the pond. There’s a path that leads close to the edge in the middle and gets you close to the stream between ponds. At the other pond, stay on the back edge and follow around. The bridge is often a productive area. Keep following around. When you reach the open area, you will probably have to go out to the sidewalk as the path inside is often overgrown early. It’s worth checking back along the other edge of the pond (especially for dragonflies) before heading back across the grassy area to the parking lot. The entire area can be covered in 30-40 minutes quickly and probably an hour thoroughly.
I’ve seen quite a variety here and think just about anything would be possible in migration. Expect warblers, shorebirds, and just about anything else. Dragonflies are common in summer (I’ve recorded over 20 species including several darners and Unicorn Clubtail) and there’s a surprising number of butterflies for an area without many flowers and open spots. Overall, I’m up to 65 birds, 23 Butterflies, and 26 Odes.