Name:  California Least Tern  (photo: U.S. Navy)
    (Sterna antillarum browni)
Status:  State Endangered (OR), Federal Endangered
Listed:  October 13, 1970
Description:  Small gray and white seabird with long, narrow, black-tipped wings and a black cap
Threats:  Habitat loss, pollution, predation

 

Overview:  The California least tern is one of the smallest members of its family, averaging only 23 cm (9 in.) in length. Typically, these terns forage in shallow estuaries and lagoons, diving head first into the water after a wide variety of small fish.  Once considered abundant, the California least tern has suffered dramatic declines due to human encroachment and destruction of its nesting habitat.  Formerly California least terns regularly nested on sandy beaches and mudflats near the ocean.  However, human disturbance related to dredging and development projects have drastically reduced tern nesting habitat.  The construction of the Pacific Coast Highway in the early 20th century had a significant impact on California least terns, as well as other shorebirds, by directly destroying nesting beaches as well as making these areas more accessible to human encroachment.  Today, the construction of housing developments continues to reduce suitable breeding grounds, and many remaining tern populations choose to nest on mudflats away from the ocean and man-made landfill instead.  These more terrestrial sites have made the nesting terns and their chicks increasingly vulnerable to predation by the red fox (Vulpes vulpes) as well as dogs, cats and raccoons.  In 1988, three Orange County tern populations suffered losses of 75% due to fox predation.  In addition, the tern’s fishing grounds have also been severely impacted by dredging, development and pollution.
 

An interesting outcome of efforts to conserve the few remaining tern nesting sites is that the U.S. Navy, the Marine Corps and the U.S. Fish and Wildlife Service have teamed up to manage a large number of California least tern populations breeding on military lands.  Because they tend to be located on remote beaches that are off-limits to the public, naval bases and training centers have become refuges for these endangered birds.  Cooperation among these government agencies to minimize human impact within these sites have resulted in a dramatic recovery of tern populations--which climbed from a low of 600 breeding pairs in 1970 to 2,300 pairs in 1993.  Today, over one-third of California least tern populations breed on Navy and Marine Corps bases.
 

Distribution: The historic breeding range of the California least tern extended along the southern California coast between Santa Barbara and San Diego, with some nesting sites documented as far north as San Francisco Bay and as far south as southern Baja California.  Today, the breeding range of these terns is limited to San Francisco Bay and a few areas along the coast from San Luis Obispo County to San Diego County.  During the winter months, they head south to the Pacific coast of Central America.  When feeding, California least terns often follow schools of fish north and may be seen fishing off the southern coast of Oregon.

 
 
 
 


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