In his paper on the changing distribution of the Western Mockingbird (Mimus polyglottos leucopterus) in California, Arnold (Condor, vol. 37, 1935, pp. 193ff) states that its breeding range in the San Joaquin Valley extends from central San Joaquin County, on the north, to south of Bakersfield. In the Sacramento Valley the same author believes the area Sacramento seems to be an extension of the breeding territory at the north end of the San Joaquin Valley, while the area about Davis, Yolo County, in which the mockingbird was first reported nesting in 1928 (Storer MS, 1933), seems to constitute a distinct area of residence, without any connection, at the present time, at least, with any other areas. It is pointed out that Marysville, Yuba County, may be a breeding area but that no records of nests have been reported since 1890 (Belding, Land Birds Pac. Dist., Calif. Acad. Sci., Occ. Papers 2, 1890, p. 226). The present writer first noted the presence of mockingbirds about his newly established residence near Durham, Butte County, during the winter months of 1932-33. On this ranch they have occurred every year since that time during the months of November, December, January, February and March. During this time they drive away nearly all other species of birds from shrubbery which has ripe fruit, particularly from the Oregon grape, Virginia creeper, pyracantha and varieties of climbing roses. The birds usually seem to leave the region about the first of March, although on another ranch about a mile away a singing bird was daily observed by the writer during most of the months of April and May, 1937. This bird sang almost hourly during the day and often on moonlight nights from the top of an old barn and from the cross-arm of a power pole. Hours were spent in searching, but no nest was ever discovered. During the spring of 1937 a student in the writer's ornithology class insisted that mockingbirds had been nesting in Corning, Tehama County, for many years. A trip to Corning during the first week of June, 1937, resulted in numerous birds being observed about the residence district of that town and about the surrounding olive orchards, but no occupied nests were found. A citizen of Willows, Glenn County, reported mockingbirds nesting at his residence since 1934. In May, 1938, the writer decided to investigate the mockingbird problem by visiting the areas where they had been reported by his students. Near Sutter, Sutter County, on the Meischke Ranch, he was shown a vacated nest which was occupied until the previous day by three young birds. The nest was collected. Another nest containing one mockingbird egg was located in a pyracantha shrub. The egg was collected. A mockingbird was singing at the time and another resented vociferously the intrusion and the taking of the egg. Mockingbirds have been reported by Mr. Meischke, the owner of the ranch, to have nested there since 1932, and the writer was shown the remains of several old nests still in their original places which were usually in thick pyracantha shrubs. In the vicinities of Durham and Chico, Butte County, no mockingbirds were seen during this trip, although the places visited in these communities usually were occupied during the winter months. Between the Sacramento River and the town of Orland, Glenn County, two mockingbirds were observed singing from the tops of power poles about a mile apart. No stops were made to look for nests until the town of Comrning, Tehama County, was reached, although three other roadside observation records of singing birds were made between Orland and Comrning. In the last named town two