Historically, two California Gull nesting colonies existed in Wyoming. In 1984 there were six breeding locations consisting of 10 different colonies that included approximately 7,273 nests. The increase in the California Gull nesting population in the state is probably a consequence of man-caused environmental changes that have resulted in the creation of additional breeding habitat and new food sources.
Findholt, Scott L.
"Status and distribution of California Gull nesting colonies in Wyoming,"
Great Basin Naturalist: Vol. 46
, Article 11.
Available at: https://scholarsarchive.byu.edu/gbn/vol46/iss1/11