Calavera Nature Preserve in Carlsbad encompasses 260 acres of protected open space off Peninsula Drive, anchored by the freshwater Lake Calavera reservoir and the extinct volcanic remnant of Mount Calavera at 513 feet. The preserve connects to more than 17 miles of multi-use trails through the adjacent Lake Calavera Preserve, forming a combined corridor for hiking, mountain biking, and leashed dog walking in east Carlsbad near Poinsettia Park. Habitat zones include coastal sage scrub, mixed chaparral, and freshwater marsh surrounding a dam-created lake that dates to the World War II era and holds roughly 400 acres of surface water. Six threatened or endangered species reside within the preserve boundaries, including Thread-leaved Brodiaea, Orange-throated Whiptail, and the federally listed California Gnatcatcher. The nonprofit Preserve Calavera advocates for the site's ecological stewardship, a conservation model that parallels the wetland education programming at Agua Hedionda Lagoon Foundation (Discovery Center) along Carlsbad's lagoon corridor. The preserve supports 115 documented plant species, 49 bird species, 10 mammal species, and 7 amphibian and reptile species across four distinct habitat zones, with the freshwater marsh providing year-round nesting habitat for egrets, herons, and migratory waterfowl.