Main Street bridge: Nothing for 25 minutes, then an adult flew out of the nest box and upstream. 5 minutes later an adult flew to the nest box from upstream. Nest seems to be active.
Bridge 3: spent 15 minutes. Nothing at first, then a bird flew upstream out of the nest box closest to the parking lot side of the bridge. A few minutes later an unbanded adult flew to the nest and the blue-banded adult flew in and stood guard until I left. Photo attached. Nest is active.
Bridge 1 and fairy pond area: no dippers seen or heard.
So thankfully Bridge 3 birds are alive and well. As with the Main St. birds the pair decided to renovate the first nest box.