Blue Oak Ranch Reserve

This 3,280-acre site sprawls across the steep slopes of Mount Hamilton just east of urban San Jose. Located on the western slopes of the Diablo Range, the reserve falls within the watershed of San Francisco Bay. Approximately two-thirds of the reserve is drained by tributaries of Arroyo Aguague, which flows into southern San Francisco Bay via Penitencia and Coyote Creeks. The bowl-shaped Arroyo Aguague catchment area is characterized by steep wooded slopes and meadows, as well as open flats dotted with oaks and coyote brush. The precipitous Arroyo Hondo is heavily wooded on north- and east-facing slopes, while western and southern exposures consist of open grassland or dense chaparral patches.

The reserve support at least 130 species of birds, approximately 41 species of mammals, 7 species of amphibians, more than 14 species of reptiles, 7 species of fish, and hundreds of species of invertebrates. Streams and about 17 ponds (Sensitive Aquatic Resource Areas) support healthy stands of riparian vegetation in addition to aquatic species. They are important habitat for migratory birds and may be migratory corridors for numerous aquatic and terrestrial animal species. At least 73 vascular plant families are found within the boundaries, almost 80 percent of which are native. Plant communities include blue oak woodland, valley oak woodland, black oak woodland, coast live oak woodland, riparian forest, chamise chaparral, Diablan sage scrub, nonnative annual grassland, wildflower field, and native perennial grassland. Four of these are threatened plant communities: valley oak woodlands, blue oak woodlands, wildflower field, and native perennial grasslands. Foothill pines occur only in the Arroyo Hondo and on the slopes above its confluence with North Creek. Chaparral patches occur on many south-facing and some west-facing slopes. Grasslands are mainly dominated by exotic annuals, but some native perennial grasses are present.