Thus far, I have seen two American Bitterns on this trip to the Gulf coast of Texas. The first one was close to the boardwalk at the Leonabelle Turnbull Birding Center in Port Aransas.
Camera, lens, and settings for the photos at this location. E-M1X camera with 300mm f/4 lens. 1/400 sec at f/5.6, ISO 2000, 1/640 sec at f/5.6, ISO 3200, 1/320 sec at f/5.6, ISO 2000, 1/320 sec at f/5.6, ISO 3200, and 1/500 sec at f/5.6, ISO 3200.