The Kendall-Frost Mission Bay Marsh Reserve protects a valuable remnant of coastal salt marsh habitats once common throughout Southern California estuaries. Despite major alterations to the surrounding land and water, this small, heart-shaped wetland at the northern edge of Mission Bay remains remarkably productive, providing rich intertidal habitats. Topography ranges from high marsh to submerged shoreline, creating a classic vertical zonation of habitats, each with its own spectrum of vegetation and invertebrates. Habitats within the site include coastal salt marsh, tidal channels, and salt flats; the adjacent Northern Wildlife Preserve contains mudflats, a sand spit, eelgrass beds, and the open waters of Mission Bay. Thousands of shorebirds visit the marsh and mudflats during annual migrations; at least two endangered bird species, the light-footed clapper rail and Belding’s savannah sparrow, rely entirely on the marsh.