Glaucous-winged Gull

Glaucous-winged Gull (Larus glaucescens) is a large North Pacific gull with pale grey wings whose tips nearly match the back, plus a heavy yellow bill. Body shape, bill structure, plumage pattern and voice provide the strongest field characters. Age, sex and season may alter its appearance, so identification should combine several features and careful direct field comparisons with similar species in the same habitat (Wikipedia, general species account).

It feeds opportunistically on marine prey, carrion and refuse and nests colonially on coastal islands and cliffs. Its movements and social behaviour vary through the year, with breeding birds generally more dispersed and non-breeding birds gathering where food is concentrated. The Korean vertebrate catalogue used for this guide records the species in South Korea (Wikipedia, general species account; Wildlife of Korea occurrence records).