Slated to become a National Wildlife Refuge (one of the few in the U.S. within an urban area), Alameda is one of the most intensely studied Important Bird Areas in the state. It is an island composed of fill, featuring about 579 acres of wetlands and grassy, ruderal areas (including former airfield) and 413 acres of open water in east-central San Francisco Bay, across from San Francisco.

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Ornithological Summary

The main attribute of this IBA is the sheer number of nesting terns and gulls which prosper due to a combination of suitable habitat, active management, and lack of disturbance. The colony of California Least Terns in Alameda has made significant contributions to this endangered species' success, for years ranking in the world?s top ten colonies for breeding pairs. In 2007 Alameda ranked 6th for breeding pairs. In 2005 Alameda ranked 4th for fledgling production. In 2004 Alameda ranked 2nd in California for fledgling production. Alameda is the largest colony north of San Luis Obispo or Santa Barbara Counties (Susan Euing, 2008). Alameda's California Least Tern population is thought to be the source for two recently established colonies at Cogswell Marsh in Hayward and at the Montezuma Wetlands Restoration project in Suisun Marsh.

Both California and Western Gull colonies are significant at the site. Total number of breeding birds at Alameda is 23 and includes species such as Horned Lark, Loggerhead Shrike, and others that are becoming rare in urban environments. American Avocet, Black-Necked Stilt, Great Blue Heron, and Canada Goose also regularly nest on Alameda.

The site provides the largest known roosting location for California Brown Pelicans in the San Francisco Bay Area. As many as 8500 pelicans have been observed at one evening roost count (July 2006), and seasonal numbers reach 1,000-3,000 pelicans roosting on the breakwater island.

Alameda is a magnet for avian predators and migratory stopovers. Beside the resident nesting pair, there are often over 20 wintering Red-tailed Hawks. Peregrine Falcons frequent the site year around. White-tailed kites, ospreys, northern harriers, burrowing owls, are regularly seen at the site.

The site continues to serve as an important reservoir of open country and water species in the Central Bay Area. Over 140 species of birds have been observed at the proposed refuge in the last few years.

With habitat enhancement the site might again host a significant Caspian Tern colony (1000 nests in 1991, but none since 1999) and serve other species in decline.

Help us learn more about the birds at this IBA! Enter your birding data online at Calfornia eBird! (

Conservation Issues

The site's largest threat is a proposed development and transfer of all refuge lands to the Veterans Administration for construction of a hospital on the property. This land use would generate multiple and significant disturbance uncompatible with the biological needs of the breeding Least Tern colony.

The crash of Caspian Tern populations has been attributed to the increase in vegetation around the nesting area, as well as to interactions between the terns and nesting gulls (California and Western). Other conservation concerns include helicopters and small aircraft making low flights over the island that disturb the nesting and roosting birds here (M. Elliot, PRBO, via email; Susan Euing 2008). Residential and commercial development presently being constructed adjacent to the base may exacerbate the problem of urban-subsidized predators (e.g. feral cats, skunks), which are currently under control. Plans to construct a golf course adjacent to the proposed refuge may present additional threats (e.g. an increase in crows and ravens, etc.). There are also toxic clean-up issues that must be resolved before the transfer is made from the US Navy to the US Fish and Wildlife Agency which may result in temporary disruption of habitat.


Owned by the United States Navy. Slated to become a National Wildlife Refuge.


Alameda is an island composed of fill. The proposed Refuge area features about 579 acres of wetlands and grassy, ruderal areas (including former airfield) and 413 acres of open water in east-central San Francisco Bay, across from San Francisco.

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