Sea & Shorebirds: Overview

National marine sanctuaries on the West Coast protect the largest concentration of breeding seabirds in the contiguous United States, and provide feeding habitat for thousands of seabirds and wintering birds on the Pacific Flyway. All five National marine sanctuaries on the West Coast have numerous programs that result in the restoration and protection of seabirds. To learn more, access this PDF (418 KB) from the West Coast Region web site.

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.

The region’s seabird and shorebird community is a mix of permanent and seasonal residents.

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.

Seabirds

Seabirds 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.

Examples include:

  • 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

Shorebirds

The 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.

Other coastal and aquatic birds include herons, ducks and rails.

Conservation and Management Issues

Human 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.

Monitoring

All three northern California sanctuaries are involved in a number of research and monitoring projects that focus on bird populations:

Cordell Bank National Marine Sanctuary

Greater Farallones National Marine Sanctuary

Monterey Bay National Marine Sanctuary