This taxon is Not Recognised as a species by BirdLife International.
Larus glaucoides (Sibley and Monroe 1990, 1993) has been split into L. glaucoides and L. thayeri following AOU (1998).
BirdLife International (2020) Species factsheet: Larus thayeri. Downloaded from http://www.birdlife.org on 03/07/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 03/07/2020.