Meet the Wildlife
Breeding Birds
Western Gull, Cassin's Auklet, Rhinoceros Auklet, Pigeon Guillemot, Brandt's Cormorant, Pelagic Cormorant, Double-crested Cormorant, Black Oystercatcher, Common Raven, European Starling, Ashy Storm-petrel (suspected in small numbers), Heermann's Gull (only two breeding attempts in the 1990s)
Pupping Marine Mammals
Harbor Seal, Northern Elephant Seal, California Sea Lion, Steller Sea Lion
Rhinoceros Auklet
Photo: Frank Balthis
The species most affected by habitat degradation on the island is a burrow-nesting seabird, the Rhinoceros Auklet (Cerorhinca monocerata). Rhinoceros Auklets are closely related to puffins, and breed on islands along the Pacific coast from California to Alaska, as well as in Russia and Japan. The Rhinoceros Auklet gets its unique name from the prominent vertical ‘horn’ which both males and females grow on their bills during breeding season. The roughly 300 individuals breeding on Año Nuevo Island are threatened by continuing erosion because they need stable soil to create nesting burrows. This species forages on the open ocean during the day, diving to catch fish and squid. They return to the breeding colony at night to provision their young, avoiding predators under the cover of darkness.
Rhinoceros auklets are listed as a California Bird Species of Special Concern due to their small population, high concentration in a restricted range, vulnerable island habitat, and ongoing mortality from oil contamination. They are also listed as a species of high priority management need by the U.S. Fish and Wildlife Service.
Read the article Squawk of the Auklet in Bay Nature Magazine
Cassin's Auklet
Photo: Shiway Wang
Also affected by the habitat degradation and eroding soils on Año Nuevo Island is the Cassin’s Auklet (Ptychoramphus aleuticus). Like the Rhinoceros Auklet, this tiny seabird excavates a breeding burrow and requires stable nest sites for its reproductive success. This species breeds on islands from Alaska to Baja California, and winters primarily on the open ocean. Cassin’s Auklets were first confirmed breeding on Año Nuevo Island in 1994. It is rare in the Californa Current for seabirds to newly colonize areas, especially in light of declining populations. Cassin’s Auklets prey on tiny fishes, squid, and krill, which they catch in diving pursuits. Variable numbers of Cassin’s Auklets on Año Nuevo year to year may be influenced by abundance of prey in nearby waters.
The main threats to Cassin’s Auklets are introduction of mammalian predators on their breeding islands and oil spills. This species will certainly benefit from habitat restoration on Año Nuevo Island, and it will be interesting to monitor its numbers as our project progresses.
Sources: Manuwal, D. A. and A. C. Thoresen. 1993. Cassin's Auklet (Ptychoramphus aleuticus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.oca.ucsc.edu/bna/species/050
Brandt's Cormorant
Photo: David Gardner
Another breeding seabird on Año Nuevo Island is the Brandt’s Cormorant (Phalocrocorax penicillatus). Brandt’s Cormorant is a large cormorant whose range is closely tied to the California Current system. This species is usually found less than 10 km from shore, and breeds mostly on small nearshore islands. It prefers flat spaces for breeding colonies, and currently breeds on the large flat terrace on the southern end of Año Nuevo Island.
Numbers of breeding Brandt’s Cormorants can vary greatly from year to year based on environmental conditions, and in optimal breeding years over three thousand individuals have bred at the Año Nuevo colony. This species is interesting to study because of its highly variable breeding success year to year. In warm water years, such as when the El Niño Southern Oscillation (ENSO) occurs, Brandt’s Cormorants tend to have much lower reproductive success, with many individuals not even attempting to breed. The sensitivity of this species to environmental conditions make it a valuable indicator of overall oceanic trends such as changes in climate and prey populations.
Sources: Wallace, Elizabeth A. and George E. Wallace. 1998. Brandt's Cormorant (Phalacrocorax penicillatus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.oca.ucsc.edu/bna/species/362
Pelagic Cormorant
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Photo: David Gardner
Pelagic Cormorants (Phalocrocorax pelagicus) utilize the human history of Año Nuevo Island—they breed on the old light keeper’s house. A small, cliff-nesting species of cormorant, Pelagics find the second-story eaves of this old house a quite suitable spot for nesting. Pelagic Cormorants are widespread in the Pacific, breeding from Alaska to Baja California, and along the Asian coast to Southern China. Despite their name, this species is not a truly pelagic bird, and prefers inshore waters no more than a few kilometers from shore.
Pelagic Cormorants are not as well studied as other related species, partly due to their nesting sites on precarious cliffs. The Año Nuevo State Reserve provides an interesting opportunity to study this species, as they nest in the reserve both on the island and on the rocky cliffs of the nearby mainland.
Sources: Hobson, Keith A. 1997. Pelagic Cormorant (Phalacrocorax pelagicus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.oca.ucsc.edu/bna/species/282
Western Gull
Photo: Shiway Wang
The most conspicuous breeding bird on Año Nuevo Island is the Western Gull (Larus Occidentalus). Though the Western Gull is an everyday sight on the Pacific Coast, this gull actually has a fairly limited worldwide range, spanning only from Baja California to Washington State. The Western Gull colony on Año Nuevo Island has numbered around two thousand individuals in recent years.
These gulls make a small scrape on the ground which is usually lined with plant material, and up to three eggs are laid. Revegetating the island with native plants will provide gulls both with more nesting material and with better windbreaks for their nests, which will alleviate the current problem of gulls nesting in the entrances of auklet burrows to escape the wind. Like other gull species, the Western Gull is ever the opportunist, and will take advantage of any and all food sources, including auklet chicks. Adult Rhinoceros Auklets fly into the colony only under the cover of darkness in order to avoid predation and food theft by the gulls.
Although the gulls present challenges to auklet breeding success, a primary goal in the our project is to manage the island for maximum biodiversity, and the gulls are an important player in the local ecosystem. Improved habitat quality on the island will be beneficial for gulls and auklets alike, and will help relieve the stresses that currently are caused by competition for space and nesting material in marginal habitat.
Sources: Pierotti, Raymond J. and Cynthia A. Annett. 1995. Western Gull (Larus occidentalis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.oca.ucsc.edu/bna/species/174
Pigeon Guillemot
Photo: David Gardner
The Pigeon Guillemot (Cephus columba) is a small alcid that breeds in rock crevices along Año Nuevo’s shoreline. This species is quite distinctive in breeding plumage, with an all black body, bright white wing patches and bright red feet. Pigeon Guillemots hunt by diving and probing the seafloor for small fish and crustaceans. They tend to stay close to shore in shallow waters with rocky substrates.
Guillemots prefer to nest in cavities, usually formed by rocky crevices in cliffs or on islands, but in the absence of suitable cavities they will excavate a burrow. Pigeon Guillemots are distributed throughout the North Pacific, with the southern edge of their range ending around the Channel Islands, CA. Generally about 20-30 individuals breed on Año Nuevo Island each year.
Guillemots prefer to nest in cavities, usually formed by rocky crevices in cliffs or on islands, but in the absence of suitable cavities they will excavate a burrow. Pigeon Guillemots are distributed throughout the North Pacific, with the southern edge of their range ending around the Channel Islands, CA. Generally about 20-30 individuals breed on Año Nuevo Island each year.
Sources: Ewins, Peter J. 1993. Pigeon Guillemot (Cepphus columba), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.oca.ucsc.edu/bna/species/049
Black Oystercatcher
Photo: David Gardner
With a dramatic red bill and bright yellow iris, the Black Oystercatcher (Haematopus bachmani) is a distinctive resident of Año Nuevo Island’s rocky fringes. This species is wedded to the rocky intertidal zone, where it forages for bivalves such as mussels and chitons, as well as other invertebrates such as crabs and barnacles. Despite its name, oysters are unimportant in the Black Oystercatchers’ diet, and are rarely taken.
Black Oystercatchers usually make their nests on gravelly or rocky shorelines, with around a dozen individuals breeding on the island in a given year. The Oystercatchers on Año Nuevo face the dual challenges of gull predation and breeding around large pinnipeds, which can crush their nests and eggs when they haul out. The main threats to this species on a population level are oil spills and introductions of predators to nesting locations.
Sources:Andres, Brad A. and Gary A. Falxa. 1995. Black Oystercatcher (Haematopus bachmani), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.oca.ucsc.edu/bna/species/155
Brown Pelican
Photo: David Gardner
Northern Elephant Seal
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