Cogswell 1948 Columbus auritus Dec. 18. Tomales Bay, Marin Co., Calif. This species was the commonest grebe on the bay, numbering at least 5x, or more probably 10x, the eared grebe. From Dr.??. Miller, Capt. Storer, & Harry Adamson I soon learned that all small Columbi with dark or medium gray on sides of the fore-neck are not eared grebes. Many of this species are quite gray there, with only the cheek pure white. The sharp line of demarcation of this cheek patch from black cap, from dusky of hind neck (usually with much narrow dark line down mape), the thicker neck, heavier bill, and the negative character of never having a "high stern" as the eared so often appears to have are about the best differentiating characters. We did not see any grebes fly until our return boat trip in late P.M., when several flew instead of diving. Perhaps this may have been a result of the rapidly falling tide, & more powerful & turbulent current.