In the course of investigating the relationships and plumage characters of the large gulls of western North America (Devillers, in prep.) a number of specimens had to be examined, and distributional data checked. Also, field studies, particularly in the San Diego region, northern Baja California, and the Salton Sea, have resulted in a better understanding of the distribution of some species. In this paper we summarize available data on winter distribution, timing of migration, abundance, age ratios, and habitat selection of the Glaucous Gull Larus hyperboreus, Thayer’s Gull Larus thayeri, Yellow-legged Western Gull Larus occidentalis livens, Western Gull Larus occidentalis occidentalis and L. o. wymani, Glaucous-winged Gull Larus glaucescens, and Mew Gull Larus canus brachyrhynchus.