Editor’s Note: The King Rail discussed in this account (R. elegans) recently has been split into two species, King Rail (R. elegans) of eastern North America and Cuba, and the extralimital Aztec Rail (R. tenuirostris) of central Mexico. See the 55st Supplement to the American Ornithologists’ Union Checklist of North American Birds, and references therein, for details. Future revisions of this account will reflect these changes.
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 twenty pairs breeding within a space having a diameter of thirty yards. -- Bachman in Bent 1926
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 1835, the King Rail is associated with fresh, 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 U.S. with strongholds along the Gulf Coast of Texas and Louisiana, and possibly Florida. Northern populations are migratory, but the specific wintering 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 a threatened or endangered species in 12 eastern and midwestern states, as well as in Canada. Research in response to these declines has shown populations in the Upper Mississippi and Illinois River valleys, as well as the Midwestern U.S., are particularly scarce. These population declines likely stem from direct loss of wetlands, but evidence in the Gulf Coast suggests that King Rails are sensitive to broad-scale changes in hydrological regimes, such as the impoundment or stabilization of water levels, that influence wetland vegetation.
Despite being a species of concern, the King Rail is a game bird in 13 Gulf and Atlantic coast states, although the species does not appear to be a common, specific target for hunters. Vernacular names for this bird 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 coastal n. Venezuela, and various species of R. longirostris sensu lato, the Clapper Rail and related taxa (Sibley and Monroe 1990). Species limits in this superspecies complex have been debated for many years (Bent 1926, Peters 1934, Oberholser 1937, Ridgway and Friedmann 1941, Hellmayr and Conover 1942, Dickerman 1971, Blake 1977, Ripley 1977, Avise and Zink 1988, Williams 1989, Olson 1997). Recent genetic analysis (Maley and Brumfield 2013) has helped split R. longirostris (as recognized by the American Ornithologists' Union (1998)) into three species, with the subspecies of R. elegans endemic to central Mexico now treated as a separate species, R. tenuirostris, the Aztec Rail (Chesser et al. 2014).