"Wherever there are extensive marshes by the sides of sluggish streams, where the bellowings of the alligator are heard at intervals, and the pipings of myriads of frogs fill the air, there is found the Fresh-water Marsh hen, and there it may be seen gliding swiftly among the tangled rank grasses and aquatic weeds, or standing on the broad leaves of the yellow cyamus and fragrant water-lily, or forcing its way through the dense foliage of pontederiae and sagittariae. There, during the sickly season, it remains secure from the search of man, and there, on some hillock or little island of the marsh, it builds its nest. In such places I have found so many as 20 pairs breeding within a space having a diameter of 30 yards." —John Bachman in Bent (1).
Similar to other rails, the King Rail is difficult to observe, but this large rail is noted for its striking appearance and loud vocalizations. First described by Audubon in 1835 (2), the King Rail is associated with freshwater, oligohaline, and brackish marshes, as well as rice fields. It feeds largely on crustaceans and aquatic insects in a variety of water bodies, including shallow flooded emergent vegetation, temporary ponds, creeks, and along the edge of ditches, lakes, and mudflats. The King Rail has a wide geographic distribution in the eastern United States with strongholds along the Gulf coast of Texas and Louisiana, and possibly Florida. Northern populations are migratory, but the specific overwintering locations of these populations remain unknown.
Despite this broad geographic range, King Rail populations have declined alarmingly in the past 50 years with the species now listed as threatened or endangered in 12 eastern and Midwestern states, as well as in Canada. In response to these declines, research has shown that populations in the Upper Mississippi and Illinois River valleys, as well as the Midwestern U.S., are particularly scarce. These population declines likely related to the direct loss of wetlands, but evidence also indicates that King Rails are sensitive to broad-scale changes in hydrological regimes, such as the impoundment or stabilization of water levels, that have a profound influence wetland vegetation.
Despite being a species of concern, the King Rail is a game bird in 13 states along the Gulf and Atlantic coasts, although the species does not appear to be a common, specific target for hunters. Vernacular names for the King Rail include marsh hen, mud hen, and rice chicken.
At least two subspecies of King Rail are now recognized: Rallus elegans elegans of North America and R. e. ramsdeni of Cuba (see Systematics). Rallus elegans forms a superspecies with R. wetmorei, the Plain-flanked Rail, of northern coastal Venezuela, and various species of R. longirostris sensu lato, the Clapper Rail and related taxa (3). Species limits in this superspecies complex have been debated for many years (1, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13). A comprehensive genetic analysis (14) led to R. longirostris, as recognized by the American Ornithologists' Union (15), being split into three species and R. elegans split into two species, with a subspecies endemic to central Mexico now treated as a separate species, R. tenuirostris, the Aztec Rail (16). Given these new species limits, R. elegans sensu stricto is now considered to be sister to R. crepitans, the Clapper Rail sensu stricto, of eastern North America and Mexico (14).