Important Bird Areas

Puente-Chino Hills

California

This low (<1500') range of hills on the eastern side of the Los Angeles Basin supports an intact mosaic of lowland terrestrial habitats, notably extensive areas of grassland and, along its southern boundary in Orange Co., coastal sage scrub. The woodland is dominated by California Black Walnut, and small patches of riparian thickets are scattered throughout the hills, particularly along Tonner and Telegraph canyons, permanent stream in the eastern portion of the hills. In the far northeast, a marshy stock-pond within the grassland of upper Tonner Canyon adds habitat diversity to this IBA.

Ornithological Summary

Several breeding species extremely rare and local in the Los Angeles area maintain small, remnant populations here, including Northern Harrier, Golden Eagle, California Gnatcatcher, Least Bell's Vireo and Bell's Sage Sparrow (Cooper 2000). Cactus Wren and Grasshopper Sparrow are more widespread in appropriate habitat throughout the hills. Locally-scarce grassland birds include Prairie Falcon (one pair breeds vic. Gypsum Canyon just to the south) and, in the far east, Vesper Sparrow and Ferruginous Hawk. Clark's Marsh Wren appears to have persisted along San Jose Creek in Diamond Bar (P. Unitt, unpubl. date, and probably also occurs in Upper Tonner Canyon at Grand Ave. (pers. obs.). The avifauna of the adjacent San Jose and Coyote Hills (Los Angeles and Orange counties, resp.), is similar, and may be considered part of this IBA.

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Conservation Issues

A southward extension of Chino Hills State Park to include the coastal sage scrub within and north of the city of Brea would substantially protect this major population area of sensitive species, particularly California Gnatcatcher and Cactus Wren. Similarly, the largest expanse of grassland in the IBA and its only large freshwater marsh, that of Upper Tonner Canyon just northeast of the Firestone Boy Scout Reserve, could either be folded into Chino Hills State Park or purchased by a conservation agency such as the Santa Monica Mountains Conservancy, which has already purchased and established several small reserves along the hills. The extensive grassland south of Rowland Heights may not be defensible from the encroachment of tract homes from all directions, though every effort should be made to establish easements here that maintain the relatively unfragmented configuration of the habitat.

Ownership

The Santa Monica Mountains Conservancy has purchased several small tracts along the hills. Much of the rest of the area is privately owned.

Habitat

This low (&lt;1500?) range of hills on the eastern side of the Los Angeles Basin supports an intact mosaic of lowland terrestrial habitats, notably extensive areas of grassland and, along its southern boundary in Orange Co., coastal sage scrub. The woodland is dominated by California Black Walnut, and small patches of riparian thickets are scattered throughout the hills, particularly along Tonner and Telegraph canyons, permanent stream in the eastern portion of the hills. In the far northeast, a marshy stock-pond within the grassland of upper Tonner Canyon adds habitat diversity to this IBA.