Tijuana Slough National Wildlife Refuge is located in the most southwestern corner of the contiguous United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It is part of the San Diego National Wildlife Refuge Complex

San Diego National Wildlife Refuge Complex

The San Diego National Wildlife Refuge Complex is a series of wildlife refuges established by the United States National Wildlife Service beginning in 1972. The complex incorporates six locations in San Diego County and Orange County in California.-History:...

. It was established in 1980.

The Slough is one of southern California

Southern California

Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...

's largest remaining salt marsh

Salt marsh

A salt marsh is an environment in the upper coastal intertidal zone between land and salt water or brackish water, it is dominated by dense stands of halophytic plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh...

es without a road or railroad trestle

Trestle

A trestle is a rigid frame used as a support, especially referring to a bridge composed of a number of short spans supported by such frames. In the context of trestle bridges, each supporting frame is generally referred to as a bent...

 running through it. This important salt marsh is surrounded by San Diego County

San Diego County, California

San Diego County is a large county located in the southwestern corner of the US state of California. Hence, San Diego County is also located in the southwestern corner of the 48 contiguous United States. Its county seat and largest city is San Diego. Its population was about 2,813,835 in the 2000...

 and Tijuana

Tijuana

Tijuana is the largest city on the Baja California Peninsula and center of the Tijuana metropolitan area, part of the international San Diego–Tijuana metropolitan area. An industrial and financial center of Mexico, Tijuana exerts a strong influence on economics, education, culture, art, and politics...

, Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

, with a population of 4.3 million people. Within this international bioregion, the refuge maintains essential habitats for many migrating shorebirds and waterfowl

Waterfowl

Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....

 along the Pacific Flyway.

Tijuana Slough provides critical habitat for the Federally-listed endangered

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 California least tern

California Least Tern

The Least Tern is a species of tern that breeds in North America and locally in northern South America. It is closely related to, and was formerly often considered conspecific with, the Little Tern of the Old World...

, Light-footed Clapper rail

Clapper Rail

The Clapper Rail is a member of the rail family, Rallidae. Some researchers believe that this bird and the similar King Rail are a single species; the two birds are known to interbreed.-Distribution and habitat:...

 and Least Bell's Vireo

Bell's Vireo

The Bell's Vireo is a small North American songbird. It is 4-3/4 to 5 inches in length, dull olive-gray above and whitish below...

, as well as the Salt marsh bird's-beak, an endangered plant species. Designated as a Globally Important Bird Area by the American Bird Conservancy

American Bird Conservancy

American Bird Conservancy is a non-profit membership organization with the mission of conserving native birds and their habitats throughout the Americas...

, over 370 species of birds have been sighted on the refuge.

The refuge's habitat and wildlife management programs focus on the recovery of endangered species through research, habitat restoration, and environmental education.

The Refuge is part of a larger unit called the Tijuana River National Estuarine Research Reserve

Tijuana River National Estuarine Research Reserve

Tijuana River National Estuarine Research Reserve is a natural reserve encompassing the Tijuana River Estuary, located on the Mexico – United States border, in Imperial Beach, California.-Access and features:...

, which is administered by the National Oceanographic and Atmospheric Administration. The Tijuana Reserve is one of 22 National Estuarine Research Reserve

National Estuarine Research Reserve

The National Estuarine Research Reserve System is a program of the United States government. The program establishes federal-state partnerships under the Coastal Zone Management Act to create a system of estuarine research reserves representative of the various regions and estuarine types in the...

s created nationwide to enhance scientific and public understanding of estuaries, and thereby contribute to improved estuarine management.