Tijuana Slough National Wildlife Refuge, Nature reserve in San Diego, United States

Tijuana Slough National Wildlife Refuge is a salt marsh in the southwestern corner of the contiguous United States, near the San Ysidro border crossing. It forms the northern part of the Tijuana River National Estuarine Research Reserve and is one of Southern California's largest remaining salt marshes with no road or railroad trestle crossing it.

The refuge was established in 1980 as part of a national estuarine research reserve system. Its creation reflected growing recognition that coastal wetlands needed legal protection from development and habitat loss.

The refuge is the northern part of the Tijuana River National Estuarine Research Reserve, one of 22 such reserves nationwide created to improve scientific and public understanding of estuaries. Its habitat and wildlife programs focus on recovering endangered species through research, habitat restoration and environmental education. The American Bird Conservancy designates it a Globally Important Bird Area.

Visit early in the morning or late afternoon when wildlife is most active and lighting is best for observing birds. The visitor center provides trail maps and guidance to help you navigate the wetland paths safely.

The site supports around 370 bird species, including rare species like the California least tern and light-footed Clapper Rail. This extraordinary diversity makes it a critical waypoint for migratory birds traveling between North and South America.