Different subspecies are recognized for Rostrhamus sociabilis according to variation in geographical range and some morphological aspects such as body size. However, the recognition of different subspecies is still debated and thus some checklists include three (see Clements Checklist, 2013) and others four (see Encyclopedia of Life, 2014 or Avibase, 2014):
major (Nelson & Goldmann, 1933): from Mexico to Guatemala
plumbeus (Ridgway, 1874): found in Florida and Cuba
sociabilis (Vieillot, 1817) : occurs from southern Central America (Nicaragua and Honduras) to southern South America (Brazil and northern Argentina)
levis (Friedmann, 1933): least accepted division of Snail Kites, it differentiates populations in Cuba from those in Florida
The Snail Kite, previously known as the Everglades Kite, is the only species of the genus Rostrhamus. It is part of the Accipitridae family, which also includes hawks, eagles and Old World Vultures. Accipitridae, most closely related to the Osprey (Pandionidae) than all other land birds, has been traditionally classified into different subfamilies that vary according to the author (Griffiths et al., 2007) and the type of morphological, behavioral, ecological or molecular characters used (see for example Lerner et al., 2005; Wink, 2004; Holdaway, 1994). Placing of the Snail Kite seems to be problematic and unresolved. Regarded as a milvine kite by Peters (1931), an accipiter by the South American Classification Committee (2014) and also as part of the larger buteonine assemblage by Griffiths et al. (2007), its phylogenetic position within the family remains unresolved.