Date of this Version
Ring-billed Gull Larus delawarensis and California Gull L. californicus populations have increased throughout the western United States in close association with human settlement (Conover 1983; Ryder 1993). On Upper Nelson Island in the Columbia River, the number of Ring-billed and California Gull nests increased from 4 600 in 1978 to 21 000 in 1999 (Thompson and Tabor 1981; Pochop, this manuscript). Agriculture and landfills provided food sources, and construction of reservoirs increased island nest sites for gulls (Ryder 1993). Gulls gather below hydroelectric facilities in the spring to feed on migrating juvenile salmonids (Steuber et al. 1995). Also, increased gull populations present bird-aircraft strike hazards, create nuisances and potential threats to public health, and damage cherry orchards (Greenhalgh 1952; Blokpoel and Strugger 1988; Blokpoel and Tessier 1992; Gabrey and Dolbeer 1996; Hatch 1996).