Hawk Hill is a magnificent remnant hilltop dune with ocean views of southwestern San Francisco. The shifting sand supports a wide variety of dune plants, including the locally rare California croton and the San Francisco wallflower. The brightly colored, nickel-sized green hairstreak butterfly is found in only two regions within the city: the coastal bluffs of the Presidio, and along the ridge of Golden Gate Heights, here in this and the nearby Rocky Outcrop natural areas. The goal of the Green Hairstreak Project is to reconnect and expand the populations found here so they can interbreed; the group leads spring walking tours of the neighborhood to look for the butterflies.
Before western San Francisco was settled, ocean winds deposited sand on Hawk Hill from dunes to the west of the park. Now development has spread over most of the Sunset District over the dunes west of Twin Peaks dunes, leaving no source of sand to replenish Hawk Hill. Because of the sensitivity of this site and the potential for erosion, there are no designated trails and public access is discouraged.