Like other wrens, Marsh Wrens are usually polygamous with single males building multiple nests in the hope of attracting multiple females. Male Marsh Wrens spend an enormous amount of time and energy singing and building nests. The lower photo shows the brightly colored mouth lining.
I used spot metering, aperture priority, F2.5, ISO 80 and shutter speed 1/1600. Digiscoped with Panasonic DMC-LX5 | Nikon FieldScope III | 30XWA | hand-held (no adapter)