I saw a wader / sandpiper yesterday on the Sheepscot River in Alna.
It looked bigger than a semi-palmated, it did bob its head a bit, but not repeatedly. Shorter black bill, black legs, soft mottled breast that seemed to have a subtle divide at center, and did not carry down too far, then a very clean break to a white belly and under tail. It looked like the wings extended beyond the tail. A slight eye ring, also a bit of a white smudge at the lore. Seemed to me to look more grey than brown, but the sunlight was quite harsh on it.
I'm thinking it was a Baird's Sandpiper?
It hung out on a rock for a good while, it wasn't trying to feed, just resting. The river is quite low there, about 2 feet.
I posted a few not great photos I got using my iPhone through my binoculars.