Anguilla, Antigua and Barbuda, Argentina, Bahamas, Barbados, Belize, Bermuda (B), Bolivia, Brazil, Canada (B), Cayman Islands, Colombia, Costa Rica, Cuba, Dominica, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Jamaica (B), Martinique, Mexico, Montserrat, Nicaragua, Panama, Paraguay, Peru, Puerto Rico, St Kitts and Nevis, St Lucia, St Vincent and The Grenadines, Suriname, Trinidad and Tobago, Turks and Caicos Islands, USA (B), Venezuela.
Vagrant to Iceland, Morocco, Portugal, St Pierre and Miquelon (P), Virgin Islands (British), Virgin Islands (U.S.).
Population
Estimated population is 130,000 (2010).
Least Bittern (Ixobrychus exilis) [XC368410]
by Russ Wigh from Sabine Nature Trail loop, Cameron Parish, Louisiana, United States (song)
Least Bittern (Ixobrychus exilis) [XC489348]
by Henry Miller Alexandre from Tres Rios Overbank Wetlands, Maricopa County, Arizona, United States (call)
Subspecies
Forms superspecies with Little Bittern (Ixobrychus minutus) and Yellow Bittern (Ixobrychus sinensis).
The following 6 subspecies are recognised:
exilis (Gmelin, 1789) - South-eastern Canada and eastern USA, western USA to Baja California, central America and Caribbean.
pullus van Rossem, 1930 - North-western Mexico.
erythromelas (Vieillot, 1817) - Eastern Panama through Guianas to south-eastern Brazil and Paraguay.