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Woodland of mixed pines and oaks is familiar mountain scenery in Mexico, whence it extends into southeastern Arizona along with many kinds of Mexican birds. This woodland occupies a belt from about 5500 to 6500 feet in elevation between encinal (oak woodland) below and ponderosa pine forest above. It combines tree forms of both these zones so as to make a smooth transition between them. The present report com- pares the numbers of each species of breeding bird in a series of stations, within pine-oak woodland, which were visited in the summers of 1951, 1952, and 1953. These sites extend from the Pinaleno and Santa Catalina mountains in Arizona south into central Sonora and to the Sierra Madre Occidental of northwestern Chihuahua. The stations were selected in relatively flat terrain in well-developed pine-oak woodland where there was water and a good place to camp. The stations differed in the following ways which affected the local occurrence of birds: steepness,whether on a ridge or in a canyon, amount of water and riparian vegetation, stature and spacing of trees, amount of grass, and proximity to coniferous forest.