The data set consists of data to evaluate bias in roadside surveys of secretive marsh birds in 2008 and 2009 in wetlands in the Prairie Pothole Region of Minnesota, North Dakota, and South Dakota during three survey periods (survey number). The data set includes detection values (species heard, species seen, species seen and heard) of seven focal marsh bird species (four-letter alpha codes and scientific names [genus and species]) by paired basin regime (temporary, seasonal, semipermanent, lake) locations using play-callback recordings and passive listening, and the detection distance to each species. In conjunction with surveys of wetland birds, the following location, weather and wetland features were recorded: date, route, observer, station, basin number, site location, state, time, wind, sky, temperature, background noise, comments, percent full, wetland id, emergent vegetation, height, and density, open water, floating vegetation, mudflat, upland habitat, cover class, woody vegetation and bare ground within 50 m of the survey point.