Winds prevail from the northwest in the winter which brings nutrient rich waters from the Pacific Ocean into the Gulf of California, but during the summer the winds prevail from the south having the opposite effect on the currents. San Lorenzo Marine Archipelago National Park has unique ecosystems and habitats. These ecosystems support a great nutritional pyramid important to marine animals, birds, and surrounding human settlements. The rich waters of the Gulf of California is home to over 800 species of fish and 2,000 species of invertebrates. The islands may seem barren due to the lack of fresh water and arid conditions allowing only a few desert shrubs and cactus. The marine flora consists of several varieties of algae. The algae serves as an ideal habitat for small marine species. The fauna consist of the following list of endangered species: blue whale, humpback whale, killer whale, sperm whale, green turtle, hawksbill turtle, olive ridley turtle, totoaba. The ecosystem of the San Lorenzo Archipelago consists of many varieties of commercially important fish. Swordfish, hake fish, risso dolphin are also common in the waters surrounding the islands. Rasa Island is an important nesting site for Heermann's gull, elegant tern, American oystercatcher, Craveri's murrelet, and brown pelican. Heermann's gull and elegant tern are estimated to reach 260 thousand and 200 thousand respectively which accounts for about 95% of the total world population of that species. Salsipuedes Island, Las Animas Island, and San Lorenzo Island are important reproductive habitat for the brown pelican in the Gulf of California. An average sum of nesting pairs of brown pelicans on the three islands is estimated between 6,000-18,000. The islands also sustain a great number of bird species consisting of native species and migratory species that are attracted to the rich marine ecosystem. Some of the most observed species of birds include: Cooper's hawk, golden eagle, peregrine falcon, Columbidae, magnificent frigatebird, brown pelican, and Nazca booby.