This Important Bird Area refers to a biologically diverse area of ridges and valleys at the southern end of the northern Coast Range, mid-way between Napa Valley and the Sacramento Valley. Typically "Californian", this rugged country of oak and mixed-conifer woodland, broken by grassland, chaparral, and rocky outcrops, is dominated by giant Lake Berryessa (13,000 acres), a reservoir formed by a dam on Putah Creek. Smaller Lake Hennessey (850 acres) to the west, managed by the City of Napa for water supply, has similar habitat, though on a smaller scale. Berryessa is managed by the federal government (Bureau of Reclamation, BLM) within an area designated the Berryessa Blue Ridge Natural Area, though the surrounding hills are actually mosaic of state, federal and private lands, including several jointly-managed conservation reserves (e.g. Quail Ridge Reserve on the south shore of the lake).

Ornithological Summary

Owing partially to the inaccessibility of much of this Important Bird Area, its avifauna is notable for the abundance and diversity of nesting raptors, which includes c. 10 pair Osprey and 3 pair Bald Eagle between Berryessa and Hennessey. Golden Eagle and both Peregrine and Prairie falcons breed in the rock outcrops of Blue Ridge, just east of Lake Berryessa, and forage widely. Grazing was recently eliminated from the draw-down area on the eastern shore of the lake, which has allowed a lush grassland to develop, ideal for breeding Northern Harrier. Napa-Solano Audubon is currently monitoring its progress. Other scarce open country birds increasingly rare in the region include Burrowing Owl (winter only) and Loggerhead Shrike. Both lakes support small Great Blue Heron rookeries (<15 nests, Robin Leong). Berryessa supported Purple Martin until their nest trees, snags in a flooded riparian area of the lake, eventually rotted and fell (Robin Leong).

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Conservation Issues

Long the focus of conservation attention and extremely unsuitable for residential development, much of this Important Bird Area is considered well protected. However, persistent issues include localized human disturbance of nesting raptors, particularly around areas with high visitation (e.g. Lake Berryessa).

Ownership

Lake Hennessey is managed by the City of Napa for water supply. Berryessa is managed by the federal government (Bureau of Reclamation, BLM) within an area designated the Berryessa Blue Ridge Natural Area, though the surrounding hills are actually mosaic of state, federal and private lands, including several jointly-managed conservation reserves (e.g. Quail Ridge Reserve on the south shore of the lake).

Habitat

This IBA includes rugged country of oak and mixed-conifer woodland, broken by grassland, chaparral, and rocky outcrops, is dominated by giant Lake Berryessa (13,000 acres), a reservoir formed by a dam on Putah Creek. Smaller Lake Hennessey (850 acres) to the west has similar habitat.

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