Important Bird Areas

Half Moon Bay, CA MAMU

California

The Half Moon Bay, CA MAMU IBA occupies 105 hectares of pelagic open water habitat. The IBA is located in the Northern California ecoregion. Half Moon Bay is located 25 miles south of San Francisco City off the coast of Half Moon Bay City in San Mateo County. Pillar Point Harbor is located on the northern end of the bay. It is a protect harbor with dikes built to make a protective landing.

It is owned and managed as: state-other, and has the following primary uses: other and tourism/recreation-other.

Half Moon Bay, CA MAMU is an IBA for the following species: Marbled Murrelet. It contains an estimated 10 Marbled Murrelet (breeding). The following species are on the Audubon WatchList: Marbled Murrelet.

Ornithological Summary

Half Moon Bay, CA MAMU is an IBA for the following species: Marbled Murrelet. It contains an estimated 10 Marbled Murrelet (breeding). These surveys were conducted between 2007 and 2009. The following species are on the Audubon WatchList: Marbled Murrelet.
Marbled Murrelets are small, dove-sized seabirds with a diverse breeding range between central California and Alaska. Marbled Murrelets are unique birds in that they nest in trees in close proximity to the ocean where they feed. Instead of nesting in large colonies like most seabirds, these birds nest in solidarity or in loose aggregations in the upper, broad branches of coniferous tress. Due to various reasons, population numbers have been declining in recent years (Books). In 1992, Marbled Murrelets were federally listed as a threatened species (U.S. Fish and Wildlife Service 1992). The total North American population is between 263,000-841,000 individuals with a separate subspecies and population in Russia (Ralph 1995). Marbled Murrelets nest in trees along the coast and the forage and winter off the coast of Northern America. In the summer, the murrelets feed in bays, inlets, fjords and open ocean between 5-50 meters from the coast. In California, Oregon, Washington, and British Columbia the birds remain closer to shore, mostly around 5 meters. The birds prefer shallower waters, between 20-80 meters. The largest populations exist in Prince William Sound, Kodiak Island Archipelago and further south along the British Columbia coast. Outside of these areas the populations become more disjointed and scare, largely due to availability of nesting sites. The total Marbled Murrelet population is estimated to range between 263,000-841,000 individuals (Ralph 1995). In California, the population is about 6,450 (Ralph and Miller 1995). Half Moon Bay has a total of 763 Marbled Murrelets feeding in the bay.

Conservation Issues

The decline has been attributed to a number of factors including reduction and fragmentation of old growth forests, increased predation, pollution, and mortality from fishing nets (Burket 1995). The smaller, more southern subpopulations are more at risk (Piatt and Naslund 1995). Oil spills also pose a threat to populations. Because of foraging close to shore and small body size, Marbled Murrelets are extremely high risk. Also because of their disjunct range, a large spill could wipe out many of the smaller populations. For example, the Exxon Caldez spill killed 3.4% of the Alaskan population (Carter and Kutltz 1995). The Apex Hudson Oil Spill also killed a significant number of Marbled Murrelets in California. Other pollutants and toxins are present are present from oil transport and development, mining, and pulp mills (Carter and Kuletz 1995, Fry 1995, Speckman 1996). Disturbances are another threat including; disturbance at the nest sites from airplanes, aircrafts, and boats, logging at nest sights and disturbance from traffic on local highways (Kuletz 1996 and Speckman 1996; USFWS 1992). Fishing causes significant mortalities to the Marbled Murrelet population especially in gillnets. About 0.5-2% of the Alaskan population and 6.2% of the British Columbian population are killed each year. Fewer numbers are killed in Oregon and California because of the ban on gillnets (Carter 1995; Piatt and Naslund 1995). Although data is lacking, these is significant evidence that suggests the populations are drastically declining by up to 50% in the last 10-20 years (Piatt and Naslund WB).

Ownership

The Half Moon Bay, CA MAMU IBA is owned and managed as: state-other.

Habitat

The Half Moon Bay, CA MAMU IBA is characterized by the following habitat types: open water. The IBA is located in the Northern California ecoregion. Half Moon Bay is a headland bay beach located just south of San Francisco. The bay has significant amounts of fog and is characterized by mild temperatures year round.

Land Use

The Half Moon Bay, CA MAMU IBA is used for: other and tourism/recreation-other.