Abundance and species composition of marine birds are specific to different oceanographic regions; these in turn are defined by characteristic physical and biological conditions. This has been discussed most graphically by Murphy (1936, 1967), Kuroda (1955), Sanger (1970, 1972), and Shuntov (1972). Ideally, biologists should be familiar with the physical and biological environmental factors affecting the occurrence of marine birds, since the diversity of environmental conditions that often occur over equal areas on land is not present.