Sugarloaf Rock

Sugarloaf Rock, some 300 meters (1,000 feet) off Cape Mendocino, constitutes one of the major sea-bird rookeries in the State. On its steep-sided slopes are found breeding colonies of at least seven species of birds. They are the Western gull, Larus occidentalis, double-crested cormorant, Phalacrocorax auritus, Brandt's cormorant, Phalacrocorax penicillatus, pelagic cormorant, Phalacrocorax pelagicus, black oystercatcher, Haematopus bachmani, pigeon guillemot, Cepphus columba, and tufted puffin, Lunda cirrhata. This is one of the few breeding sites in the State for the puffin.

The rock is an important resting place for wintering male California sea lions, Zalophus californianus. It is also the only known breeding site for the Steller sea lion, Eumetopias jubata, in Humboldt and Del Norte Counties.

Vegetation is sparse and occurs in the soil pockets between the broken rocks. Three distinct vegetative types have been noted, one dominated by Dudleya sp., another by Carpobrotus chilensis, and the third by mixed herbs with Synthyris sp., Eschscholzia sp., and others.

The rock is composed of Cretaceous marine sedimentaries.

Integrity: Virtually undisturbed; the island is included in a proposed Federal wildlife refuge.

Use: Research, educational, observational.

Ref: Osborne, T. O., 1972. Ecology and Avian Use of the Coastal Rocks of Northern California. Unpub. M.A. Thesis, Humboldt State University, 215 pp.

July 1977