Northern Prairie Wildlife Research Center
Habitat and History. Ring-billed and California gulls were common and scattered throughout the prairie pothole region before settlement, but populations seemingly declined greatly after settlement when many nesting colonies were eliminated by humans (Stewart 1975; Salt and Salt 1976). Gull eggs were harvested by humans and even served as food in hotels (Houston and Bechard 1982). Nevertheless, large gulls remained common in many areas (Judd 1917; Mitchell 1924; Taverner 1926; Farley 1932; Todd 1947; Bent 1963).
During the last several decades, nesting colonies of ring-billed and California gulls became established in many locations in the region and populations of both species are increasing (Stewart 1975). Nesting colonies, mostly of ring-billed and California gulls, are presently scattered throughout most of the region (Stewart 1975; Salt and Salt 1976; South Dakota Ornithologists' Union 1991). Ring-billed gulls are more abundant than California gulls, especially in eastern parts of the region (Houston 1949; Vermeer 1970; Stewart 1975; Callin 1980; South Dakota Ornithologists' Union 1991).
Population Structure. Ring-billed and California gulls are colonial nesters and sometimes travel 30 km or more from nesting colonies to feed (Stewart 1975). Colonies in areas with both species are usually a mixture of the two species although interspecific nest segregation is considerable (Vermeer 1970; Stewart 1975).
Stewart (1975) identified 11 nesting colonies in the prairie pothole region of North Dakota in 1950-72; populations of 5 were mixed and populations of 6 were only ring-billed gulls. Vermeer (1970) identified 22 nesting colonies (nearly all had both species) in the prairie pothole region of Alberta in 1967. Nesting colonies of both species are also in Saskatchewan and Manitoba (Godfrey 1986). Nesting colonies often contain several hundred to several thousand nests (Anderson 1965; Vermeer 1970).
Distribution and Abundance. We did not include ring-billed or California gulls in our surveys, but both species were numerous in two study areas (Gayford, Hay Lakes) and were regularly seen in two others (Leask, Shamrock). A large colony was on four small islands in a lake 2 km north of one of the former (Gayford; 3 km southwest of town of Irricana). A search of two islands on 28 May 1985 revealed 2,944 nests of California gulls but none of ring-billed gulls. More nests seemed to be on the other two islands; the estimated population on one island was two-thirds California gulls and one-third ring-billed gulls. One study area (Hay Lakes) is about 5 km south of Miquelon Lake where several hundred ring-billed and California gulls nested each year 1964-67 (Vermeer 1970). In one study area (Leask), large gulls came from undetermined locations to feed in a landfill. Large gulls in another study area (Shamrock) probably came from Lake Chaplin and Old Wives Lake, 20-30 km away. Large gulls were not abundant in other study areas in Canada.
No data were obtained about the abundance of large gulls in the Central Flyway study areas, but large gulls were occasionally seen in several small unit management study areas.