Anguilla, Antigua And Barbuda, Aruba, Bahamas, Barbados, Belize, Bermuda, Canada (B) (NB) (P), Colombia, Costa Rica, Cuba, Dominica, Dominican Republic, Guadeloupe, Haiti, Martinique, Mexico, Montserrat, Netherlands Antilles, Panama, Puerto Rico, St Kitts And Nevis, St Lucia, St Vincent and The Grenadines, Turks and Caicos Islands, USA (B).
Vagrant to Belgium, Czech Republic, Denmark, France, Greenland, Iceland, Ireland, Israel, Japan, Morocco, Netherlands Antilles, Norway, Portugal, Spain, St Pierre and Miquelon (NB) (P), Sweden, United Kingdom.
Western Alaska and southern British Columbia east to eastern Quebec, and possibly northern Maine. Winters along Pacific coast south to Mexico (Sinaloa) and on Atlantic coast to Florida and Greater Antilles; in mild winters from Great Lakes to Gulf of Mexico.
 
Population
Estimated population is 260,000 - 530,000 (2010).
Bonaparte's Gull (Chroicocephalus philadelphia) [XC686188]
by Manuel Oudard from Edmonds, Snohomish County, Washington, United States (call)
Bonaparte's Gull (Chroicocephalus philadelphia) [XC323029]
by Janine McCabe from Smith Lake park, Fairbanks, Fairbanks North Star, Alaska, United States (call)