The recent increase in sightings of Yellow-billed Loons (Gavia adamsii) along the Pacific coast of the contiguous United States (Remsen and Binford MS) has necessitated a revaluation of the characters used for identification, both in the field and in the hand. Field guide treatment is often inaccurate and invariably incomplete, especially in regard to birds in gray-brown plumage. The more technical literature not only is widely scattered and poorly digested for use in modern field identification, but also neglects some of the most important distinguishing characteristics.