Revisiting the Past: Historical Status of Breeding Ring-billed and California Gulls in the Klamath Basin, Oregon

Abstract

Three summaries of the historical and recent status of breeding Ring-billed (Larus delawarensis) and California (L. californicus) gulls in Oregon mention just two colony sites in the Klamath Basin—Upper Klamath Lake and Spring Lake—and lack numerical data for individual colonies. Nevertheless, nesting of gulls at Lower Klamath Lake before its water source was cut off in 1917 is well documented. Egg-set records, published literature, and archived field notes attest to nesting of both species before 1954 at two additional sites in the Klamath Basin, the Link and Klamath rivers. The largest known colonies up to that time were at Lower Klamath Lake (~2000 pairs, perhaps many more) and along the Klamath River below the town of Klamath Falls (~2000 pairs). Gulls no longer nest at these five sites, but, since at least 2000, they have nested intermittently at Swan Lake and Gerber Reservoir. Though Gabrielson and Jewett (1940) considered the California Gull more abundant in southeastern Oregon than the Ring-billed, egg-collectors’ data from 1926 to 1953 suggest the opposite, as in northeastern California. The California Gull may have been the more numerous of the two in the Klamath Basin when nesting and foraging habitat was dominated by wetlands, but the drying of Lower Klamath Lake and the great expansion of irrigated agriculture starting in the 1920s may have favored the Ring-billed. Trends in the Klamath Basin’s gull populations are unclear, but much nesting habitat has been lost. Documentation of the historical record of nesting gulls and other waterbirds is critical, as conservation efforts typically aim at restoring populations to some historical baseline, which can gradually shift lower with further declines and successive generations accepting a new status quo.