Patelka 1946 June 23 2 mi E, 1 mi S Steamboat Springs, 5000 ft., Washoe Co., Nev. Myiarchus cinerascens, Empidonax traillii; Thryomanes bewickii, Turdus migratorius, Sturnella neglecta, Eurhages cyanoccephalus, Capodocus mexicanus, and Pipilo maculatus. In the afternoon, I drove south to Carson City watching the distribution of the pinon-juniper. It had been my belief earlier, that the Truckee-Washoe-Carson valley formed the barrier separating the Sierra Nevada populations of J. coeruleusens, here occurring in the Carson Range, from the Great Basin populations. At present, it appears that these lowland areas may still at least partial, act as barriers, and that the explanation: the occurrence of "superciliosus" to be in the lower Virginia Range for continuity is sought in the relative continuity of the pinon-juniper northward along that range and thence westward via Stateline Peak (8009 ft.) onto the Sierra Nevada. The barren sagebrush country north of Reno/the Truckee Meadows would appear to form an effective local barrier fully as effective as the Owens Valley. Southward, however, the Virginia Range is more accessible to birds from the Carson Range, and vice versa. In the region of the Steamboat Hills, pinon-juniper occurs