Farallon National Wildlife Refuge
Map SatelliteThese islands, some 43 kilometers (27 miles) west of San Francisco, comprise the largest sea bird rookery south of Alaska, with over 200,000 birds at the peak of the breeding season.
Twelve species nest on the islands, the most abundant being Cassin's auklet, Ptychoramphus aleuticus, with a breeding population estimated at 140,000. Others include the Western gull, Larus occidentalis, Brandt's cormorant, Phalacrocorax penicillatus, double-crested cormorant, Phalacrocorax auritus, pelagic cormorant, Phalacrocorax pelagicus, common murre, Uria aalge, pigeon guillemot, Cepphus columba, tufted puffin, Lunda cirrhata. Leach's petrel, Oceanodroma leucorhoa, ashy petrel, Oceanodroma homochroa, black oystercatcher, Haematopus bachmani, and only in the past few years the rhinoceros auklet, Cerorhinca monocerata.
During the fall and winter months the endangered brown pelican, Pelecanus occidentalis californicus, and peregrine falcon, Falco peregrinus anatum, are frequently sighted. Additionally over 200 species of birds have been identified here, several of them being the first sight records in the State.
In addition to the birds, three pinnipeds have established rookeries on the island, the California sea lion, Zalophus californianus, Steller sea lion, Eumetopias jubata, and, since 1972, the Northern elephant seal, Mirounga angustirostris.
Vegetation is sparse on the islands, with the most common plant being the Farallon weed, Lasthenia maritima, which is used by many of the birds as nesting material. The sand spurrey, Spergularia macrotheca, is also present, as are a number of introduced species.
Geologically, the islands are granitic outcrops and have affinities with the Salinian belt of the Sur-Nacimento fault region found to the south on the mainland and with the granite found to the north at Point Reyes and Bodega Head. The islands exhibit various geomorphic features including numerous sea terraces, huge sea caves, and both relict and present-day surge channels. On portions of the islands guano deposits are over 30 centimeters (1 foot) deep.
Integrity: After a long history of plunder which exterminated the sea otter and elephant seal and caused several bird species to cease breeding here, the islands are now protected and are returning to their former status, as the mammal and bird species are returning to former population sizes and "re-colonizing" them. Unfortunately, the European hare was introduced on the large Southeast Farallon and is still present. Permanent human habitation ended when the Coast Guard automated the light station in 1972; though there are still buildings, they are used only by research scientists. The Middle and North Farallons have never been inhabited, the latter being virtually inaccessible and the former frequently awash as is Noonday Rock, the northernmost part of the Refuge.
Use: Research. Public access is prohibited and permission must be obtained from the United States Bureau of Sport Fisheries and Wildlife.
Ref: Hanna, G. Dallas, 1954. Geology of the Farallon Islands in Geologic Guidebook to the San Francisco Bay Counties, California Division of Wines Bull. 154, San Francisco.
Blankenship, J. W. and Charles Keeler, 1892. Natural History of the Farallons. ZOE Vol. 3, p. 144-165.
March 1975
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman