Occurrence and Migration of Certain Birds in Southwestern California

last published summary by Grinnell and Miller (1944). A subject still in need of intensive study is autumnal migration. Facts about the timing of movement of individual species and of migrant waves are poorly known for birds in general, but especially so for the western wood warblers (Parulidae). The belief that there are no waves of warblers in the western United States is commonly accepted. Intensive study of a small area in the fall of 1962 has brought out some new facts concerning both the movements of common western species and the occurrence of several eastern species considered to be casual or accidental in California. The study area reported on here, referred to as the Tia Juana River bottom, encompasses the terminal five miles of that river. The Tia Juana River originates in the coast ranges of southern San Diego County, California. It flows southwestward into northern Baja California, Mexico, but swings to the northwest near Tijuana and empties into the Pacific Ocean in extreme southwestern San Diego County. The study area, about four miles square, is bounded on the north by San Diego Bay, on the east by U.S. Highway 101, on the south by the international border, and on the west by the Pacific Ocean. Most of our work was concentrated in favorable areas within a mile of the river. This section of the flat coastal plain is one of truck farming and small dairy ranches. The river, in the center of the area, is dry most of the year and consists mainly of a sandy wash with low brush and weeds growing in and along it. Migrant birds tended to concentrate on the Myers property, so extensive observations were made there. The property is about one mile south of Nestor, on the north bank of the wash. Several rows of tamarisk trees (Tamarix sp.) border the property, and a shallow ditch grown to low brush, especially tree tobacco (Nicotiana glauca), runs along the northern edge of the place. A small fish pool provides a constant water supply for birds. The property is approximately 300 x 200 feet (91 x 61 m). This clump of greenery is the only prominent stand of vegetation in the valley.