Range map of both Common Gull (Larus canus) and Short-billed Gull (Larus brachyrhynchus).   Breeding  Year-round  Nonbreeding
Adapted from: 

BirdLife International. 2016. Larus canus. The IUCN Red List of Threatened Species 2016: e.T22694308A86717781. https://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22694308A86717781.en. Downloaded on 09 June 2018.
Common Gull. William Moskoff, Louis R. Bevier, and Pamela C. Rasmussen. https://birdsoftheworld.org
Short-billed Gull. William Moskoff and Louis R. Bevier. https://birdsoftheworld.org
Cephas