Systematics

Originally described as Larus modestus von Tschudi, 1843, Archiv Für Naturgeschicte 9: 389 (10 von Tschudi, J. J. (1843) Diagnosen einiger neuer peruanischer Vögel. Archiv Für Naturgeschichte 9(1-2):385-390 Close ). Most recent authorities place this species, along with Franklin's Gull (Leucophaeus pipixcan), Dolphin Gull (Leucophaeus scoresbii), Laughing Gull (Leucophaeus atricilla), and Lava Gull (Leucophaeus fuliginosus), in the genus Leucophaeus (the “hooded gulls”; 11 Pons, J.-M., A. Hassanin, and P. A. Crochet. (2005). Phylogenetic relationships within the Laridae (Charadriiformes: Aves) inferred from mitochondrial markers. Molecular Phylogenetics and Evolution 37(3):686-699. Close , 12 Dickinson, E. C., and J. V. Remsen (Editors) (2013). The Howard and Moore Complete Checklist of the Birds of the World. Fourth edition. Volume 1. Aves Press, Eastbourne, United Kingdom. Close , 13 Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, J. A. Gerbracht, D. Lepage, B. L. Sullivan, and C. L. Wood (2021). The eBird/Clements Checklist of Birds of the World: v2021. Cornell Lab of Ornithology, Ithaca, NY, USA. Close , 14 Gill F., D. Donsker, and P. Rasmussen, Editors (2022). IOC World Bird List (v12.1). Close ), though some still place the species in an expanded Larus (e.g., 15 del Hoyo, J., and N. J. Collar (2014). HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1. Non-passerines. Lynx Edicions, Barcelona, Spain. Close ). Previously thought to be most closely related to Heermann's Gull (Larus heermanni).

There is no geographic variation known.

Gray Gull appears to be most closely related to the largely allopatric Dolphin Gull (Leucophaeus scoresbii) (11 Pons, J.-M., A. Hassanin, and P. A. Crochet. (2005). Phylogenetic relationships within the Laridae (Charadriiformes: Aves) inferred from mitochondrial markers. Molecular Phylogenetics and Evolution 37(3):686-699. Close ). Together, these two species appear to be sister to the clade that includes Laughing Gull (Leucophaeus atricilla), Franklin's Gull (Leucophaeus pipixcan), and Lava Gull (Leucophaeus fuliginosus) (11 Pons, J.-M., A. Hassanin, and P. A. Crochet. (2005). Phylogenetic relationships within the Laridae (Charadriiformes: Aves) inferred from mitochondrial markers. Molecular Phylogenetics and Evolution 37(3):686-699. Close ).

Unreported (16 McCarthy, E. M. (2006). Handbook of Avian Hybrids of the World. Oxford University Press, Oxford, United Kingdom. Close ).

It is locally known as Gaviota Garuma (Chile) or Gaviota Gris (Perú, Ecuador).

Nothing known.