Geographical distribution of American herring gull.    Breeding  Year-round  Nonbreeding
BirdLife International. 2016. Larus smithsonianus. The IUCN Red List of Threatened Species 2016: e.T62030590A95186748. https://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T62030590A95186748.en. Downloaded on 04 June 2018.
Cephas