Seabirds and Shorebirds
The three northern California sanctuaries boast some of the most diverse and abundant bird life in the world. This is due to a number of reasons, such as:
- Oceanographic upwelling along the coast provides feeding grounds that are rich in zooplankton and small fishes. (During the upwelling season, the highest levels of seabird biomass in central California waters are found at Cordell Bank, Monterey Bay and the Farallon Ridge.)
- The nearby land provides excellent nesting habitat for many species.
- The region is a convenient stop-off point for migrating birds that come from temperate areas in Chile, New Zealand, Hawaii and other locations.
- The proximity of very deep water close to the shallow feature of Cordell Bank creates unique local conditions for high productivity and optimal conditions for seabird foraging.
Sanctuary waters are also important to several species that are considered of special concern because of their reduced or declining populations. Those that appear in at least two of the three sanctuaries include the Marbled Murrelet, the Western Snowy Plover , the Black-Footed Albatross, the Ashy Storm-Petrel and the Cassin's Auklet.
Black-bellied Plover Pluvialis squatarola, a male that is transitioning into breeding plumage.
Pied-Billed Grebe Podilymbus podiceps. Winter plumage.
SeabirdsSeabirds are those birds whose normal habitat and food source is the marine environment, whether coastal, offshore or pelagic. The majority of seabirds in this region are seasonal visitors.
They can be divided into four groups by their feeding strategies , which are reflected in their anatomy, physiology and habitat niche.
- Surface feeders: albatross, frigatebirds and pelicans
- Surface swimmers/pursuit divers: alcids, cormorants, loons and grebes
- Plunge-divers: terns, gulls, shearwaters and pelicans
- Scavengers and pirates (those who steal from other birds): gulls, fulmars, and jaegers
ShorebirdsThe term shorebird, or "wader," refers to any bird that relies on beaches or wetlands for feeding and nesting habitat. Shorebirds are also classified by their feeding strategies.
- "Probers" use their long beaks to probe down into the sand for buried clams, worms and other animals. Probers include dowitchers and sandpipers.
- "Gleaners" scurry back and forth along the beach, feeding on invertebrates they find on the sandy surface. Examples include sanderlings and plovers.
Figure 2. Marine bird biomass within the Monterey Bay, Gulf of the Farallones, and Cordell Bank National Marine Sanctuaries.[View Larger]
Conservation and Management IssuesHuman impacts to bird populations worldwide include competition for food with commercial and recreational fisheries; entanglement in fishing gear; ingestion of marine debris; and disturbance of roosting and breeding birds by watercraft, aircraft and human visitors. Environmental contamination from the historical use of pesticides may still affect some species. Oil spills are a very real danger, also.
Changes in climate and oceanographic conditions also affect bird populations. The prevalence of marine birds using sanctuary waters changes from year to year due to fluctuations in marine conditions, including El Niño, Pacific Decadal Oscillations, and changes in intensity and timing of upwelling conditions in the spring/summer.
MonitoringAll three northern California sanctuaries are involved in a number of research and monitoring projects that focus on bird populations: Cordell Bank National Marine Sanctuary
- Cordell Bank Ocean Monitoring Program
- Tracking Black-Footed Albatross Movements and Conservation
- Distribution and Abundance of Marine Birds, Mammals and Zooplankton Relative to the Physical Oceanography of the Gulf of Farallones and Cordell Bank
- CSCAPE: Collaborative Survey of Cetacean Abundance and the Pelagic Ecosystem
- Tagging of Pacific Pelagics
Gulf of the Farallones National Marine Sanctuary
- Sanctuary Ecosystem Assessment Surveys (SEA Surveys)
- Beach Watch
- PRBO Conservation Science
- Seabird Protection Network
Monterey Bay National Marine Sanctuary