Detailed studies of the underwater feeding behavior of Common Murres (Uria aalge californica) do not appear to have been reported. We had the opportunity to make such a study beginning in September 1964, when school children found an apparently uninjured murre on the beach near Humboldt Bay, California, and brought him to Humboldt State College. The bird was a nearly full-grown young male in juvenal plumage with fully developed flight feathers. Throughout the study, from 16 September 1964 to 19 January 1965, the murre was housed in a 620-gallon, indoor salt-water aquarium in the Wildlife Building at Humboldt State College. The aquarium tank is 66 inches long, 48 inches wide, and 45 inches deep and is constructed of concrete with a glass window in front 60 inches wide and 44 inches high through which detailed observations of the murre's underwater activities were made. The water was aerated with an air pipe, and filtering and refrigeration systems maintained the water temperature at 110 C. An overflow pipe opened at the surface, allowing the bird's fecal material to settle to the bottom where it could be collected for analysis. All pipes were near the tank walls and did not interfere with' the murre's activities. During most of the study period the aeration system was kept at a low enough level so that there was essentially no surface turbulence. The murre was fed live cull rainbow trout (Salmo gairdnerii) from the college hatchery. These fish averaged 25 per pound at the beginning and 10 per pound at the end of the study. Twice daily, the bird was placed in a paper bag and weighed to the nearest 5 g. Weights were usually taken about 0800 and in the late afternoon. We wish to thank the following for help with various phases of the study: R. I. Bonn, J. A. Gast, R. L. Jarvis, R. L. Ridenhour, Marilyn Sanford, R. A. Wallace, and E. A. Whitaker. R. E. Genelly and A. S. Mossman critically read the manuscript.