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The Mexican spotted owl inhabits diverse forest types scattered across an even more physically diverse landscape. Further, human activities vary dramatically throughout the owl's range. These variations limit our ability to approach status assessment on a rangewide basis. The inescapable conclusion is that the recovery effort cannot, and should not, be applied with uniform rigor across the owl's entire range. Consequently, the Recovery Team divided the range of the owl into 11 geographic areas called "Recovery Units" (hereafter RUs). Six RUs were recognized within the United States: Colorado Plateau, Southern Rocky Mountain - Colorado, Southern Rocky Mountain - New Mexico, Upper Gila Mountains, Basin and Range - West, and Basin and Range - East. In addition, five RUs were recognized in Mexico: Sierra Madre Occidental - Norte, Sierra Madre Occidental - Sur, Sierra Madre Oriental - Norte, Sierra Madre Oriental - Sur, and Eje Neovolcanico.

Recovery Units in the United States were identified based on the following considerations (in order of importance): (1) physiographic provinces, (2) biotic regimes, (3) perceived threats to owls or their habitat, (4) administrative boundaries, and (5) known patterns of owl distribution (table II.B.1). Four major physiographic provinces were used in delineating RUs in the United States: the Colorado Plateau, Basin and Range, Southern Rocky Mountain, and Upper Gila Mountain (see Hammond 1965, Wilson 1962, USGS 1970, Bailey 1980). Biotic regimes were based on classifications by Bailey (1980) and Brown et al. (1980). Administrative boundaries were used where management practices differed between jurisdictions. The following narratives describe dominant physical and biotic characteristics, patterns of owl distribution and habitat use, and the dominant patterns of land ownerships and land use within each RU.