Just some basic info. I doubt it's really necessary to ID gray fox to subspecies, and I wouldn't recommend it unless you've really familiarized yourself with the background literature.
Hall 1981. The mammals of North America. 2nd ed. John Wiley and Sons, New York. [I have this in my office.] Review https://doi.org/10.2307/1380295
Grinnell, Dixon, & Linsdale. 1937. Fur-bearing mammals of California: their natural history, systematic status, and relations to man. UC Berkeley Museum of Vertebrate Zoology. [I have this in my office.] https://search.worldcat.org/formats-editions/1836075
Miller & Kellogg. 1955. USNM Bulletin 205 List of North American Recent Mammals. USNM Bulletin 205:689 https://www.biodiversitylibrary.org/page/7670612#page/705/mode/1up
Reding et al. 2021. Mitochondrial Genomes of the United States Distribution of Gray Fox...Front. Ecol. Evol. 9:666800 https://doi.org/10.3389/fevo.2021.666800
ASM Mammalian Species account, https://doi.org/10.2307/3503957
California towhees are largely sedentary, non-migratory. Several people appear to be IDing incorrectly to subspecies presumably based on common name, i.e. Northern California Towhee (bogus).
Oberholser, H. C. 1919 Description of a New Subspecies of Pipilo Fuscus. Condor 21(5):210-211. https://sora.unm.edu/node/96240
Grinnell & Swarth. 1926. Systematic review of the Pacific coast brown towhees. Univ. of Calif. Publications Zoology https://www.biodiversitylibrary.org/item/93394#page/543/mode/1up
Grinnell & Miller. 1944. A Distributional List of the Birds of California. Pacific Coast Avifauna 11. Museum of Vertebrate Zoology, University of California. https://sora.unm.edu/node/122
Paynter, R. A., Jr. 1970. Subfamily Emberizinae. Pages 3-214 in Check-list of birds of the world. [p175] https://www.biodiversitylibrary.org/item/50593#page/191/mode/1up Cited as primary reference for subspecies by Pyle 1997.
Pyle, P. [at ppyle] 1997. Identification Guide to North American Birds. Part I. Slate Creek Press, Bolinas, CA, USA. (note: a second edition was published in 2020 which I have not seen: https://www.inaturalist.org/observations/142990418)
Benedict et al. 2020. California Towhee (Melozone crissalis'), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.Org/10.2173/bow.caltow.01
