Bay Nature magazineSpring 2006


Squawk of the Auklet

April 1, 2006

We approach Año Nuevo Island by boat, navigating the gauntlet of unpredictable swells that threaten to upend our small inflatable craft.The deafening noise from hundreds of barking California sea lions drowns out my voice. Northern elephant seals hauled out on the island’s beaches and coves add their snorts and grunts to the mix. I must shout and use hand signals to communicate the landing plan to my shipmates.

Keeping a safe distance from the intertidal reefs and surrounding islets used by harbor seals, oyster-catchers, pelicans, and pupping Steller sea lions, we land in a small cove decorated with abalone shells and parts of wrecked sailboats. As we haul our gear above the waves, the cacophony from the marine terrace above intensifies: hundreds of nesting western gulls are telling us that this island is theirs.

We climb up to the marine terrace slowly, hunched over to keep a low profile and avoid scaring off any wildlife. Before standing erect, we scan the top of the island, count the roosting pelicans and cormorants, and look for anything unusual. Sometimes rare species stop over on the island, including tropical seabirds such as brown and masked boobies. None today. But there’s no shortage of life here: Seasoned as I am to the place, I don’t notice the thick odor of rotting seaweed, bird guano, seal scat, and ripening carcasses, but a new researcher in our group can’t help but comment on the stench.

Año Nuevo Island is unlike anything that can be experienced on the mainland. It is one of only a few refuges in the Bay Area where marine mammals and seabirds can rest and rear their young in an environment safe from terrestrial predators and unfamiliar disturbances. Four species of pinnipeds (seals and sea lions) and seven species of marine birds use this island for breeding. Although small compared to the Farallones or the Channel Islands, Año Nuevo Island’s nine acres of rock and soil match and, for many species, exceed the density of wildlife on those larger islands off the California coast.

Public access to the island, north of Santa Cruz, is managed by Año Nuevo State Reserve and has been limited to regulated research activity since 1968. I am part of a group of biologists privileged to spend time on the island and learn about this unique and critical habitat. Docents and thousands of visitors on the mainland beach, who come to see the breeding northern elephant seals, often say the island looks quiet and abandoned. In vivid contrast, up close, Año Nuevo Island is noisy and packed with life.

The daytime sensory overload of sights, smells, and sounds is just the beginning. When night falls, elusive burrow-nesting seabirds – rhinoceros and Cassin’s auklets – arrive with their day’s catch, quickly heading underground to avoid the aggressive western gulls that build nests on the surface above. Researchers who spend the night sleep in drafty old lighthouse facility buildings. After dark, the three-toned calls of the Cassin’s auklets crying “let me in” come from under the building that once housed the steam-powered foghorn. Outside, a few hundred exotic-looking rhinoceros auklets, each with a horned bill and an attitude, are growling and furiously excavating 10-foot-long burrows into the island’s soil.

This colony of “rhinos”- at the southern end of their worldwide breeding range – first brought me to Ano Nuevo Island in 1992. The nickname “rhino” is not only fun but also appropriate because the birds are not true auklets. Rhinos’ larger skeletons, different foraging behavior, and genetic lineage put them squarely in the puffin tribe – the birds are more closely related to tufted puffins than to Cassin’s auklets. Yet rhinos are so unusual that they have been assigned their own genus, Cerorhinca, meaning “one horn.”

Julie Thayer, a biologist at PRBO Conservation Science, and I have followed the birds’ annual breeding cycles to better understand the ecology of this island and to track the changing marine environment. Our studies contribute new insights to the impressive collection of knowledge built since the protection and investigation of the island began in the 1960s.

California’s relatively small population of rhinoceros auklets is protected by the state as a “breeding species of special concern.” Approximately 1,700 breeding birds live on Castle Rock, the Farallones, and Ano Nuevo Island – all protected refuges. Large island colonies exist in Japan, Alaska, British Columbia, and Washington, with a world population grossly estimated at 1.5 million birds. Estimates are very rough because it’s tricky to count burrow- and crevice-nesting seabirds that run their errands at night.

While the rock layers that created Ano Nuevo Island were formed 12 million years ago, this place’s existence as a true island has been surprisingly brief. In 1603, it was still a point of land jutting out from the mainland – named “Punta de Ano Nuevo” by a Spanish expedition that sailed past. Between then and the late 1700s, rapid erosion formed a channel and cut the point off from the mainland. Even then, however, the isolation was not complete. As late as the mid-1800s, the island was still accessible by foot at low tide via the reef and sand spit.

The island ecosystem was most rapidly altered by the establishment of a lighthouse facility in the late 1800s. Seventy-five years of habitat manipulation drastically changed the island’s plant community and hastened natural erosion processes. The consequences of these changes have fallen disproportionately on the rhinoceros auklets. Their ability to live and rear their young underground on Ano Nuevo Island depends entirely on the availability of undisturbed soil and stabilizing vegetation. In 1997, a dry summer followed by record El Nino conditions, including major storms and higher than normal densities of sea lions and pelicans, nearly cleared the island of all vegetation. Over five feet of topsoil were lost, and half the nesting burrows in some areas collapsed, killing some birds.

With no other island habitat in the Central California coastal region to support this colony, researchers from several organizations embarked on a collaborative effort in 2001 to revive the native plant community on the island. Our main objective was to improve soil stability and support the survival of the rhino colony.

Ano Nuevo island
The island consists of about seven acres of eroding marineterrace and two acres of beaches and islets. In 1997, a dry summerfollowed by record El Nino storms left the island nearly bereft of allvegetation, though recent efforts have begun to restore some nativeplants. Photo by Saul Chaikin.

Historically, seabirds, seals, sea lions, and otters were more abundant in the Ano Nuevo region than they are today, as evidenced by the success of the fur trade in the early 1800s, which radically changed the distribution of some species. Recent paleontology studies reveal that before this era of intense hunting, the most abundant sea lion in the Bay Area was not the California sea lion we are all familiar with today; it was the northern fur seal (which, despite its name, is a member of the sea lion family). Fur seals were completely extirpated from Central California, but they have recently begun to recolonize a pupping site on the Farallones, 28 miles west of the Golden Gate Bridge.

Like the fur seals, rhinoceros auklets – which were seen on the Farallones in the mid-1800s – have also naturally returned to Central California after a century of absence. Rhino chicks were first discovered in burrows on Ano Nuevo Island in 1982, directly following the removal of introduced bush rabbits. Burrowing rabbits did not cause the birds’ initial disappearance, but they likely delayed new colonization on both the Farallones and Ano Nuevo by aggressively displacing the birds from potential burrows.

We do not know if rhinoceros auklets historically occupied the San Mateo coast. When rhinos were last known to breed in California in the mid-1800s, Ano Nuevo Island was still accessible by foot at low tide. If there were rhinos in the area, perhaps they dug burrows in the vertical cliffs inaccessible to coyotes and foxes, as a handful of birds still do near the Davenport pier, about 5 miles to the south.

When access to the mainland was cut off by water, the island’s plant and animal communities certainly began to change. But the ecology of the island had little time to take its natural course. The rocky coastline had become notorious for shipwrecks, and the federal government purchased the island in 1870 to install a foghorn and lighthouse. Regular human occupation began in 1904 with the building of residences for the light keepers and their families. Photos and logbooks tell us that during this time, island residents fenced off most of the marine terrace, planted flower and vegetable gardens maintained with freshwater cisterns, and discouraged marine birds and seals from sharing the humans’ backyard. When the Coast Guard closed the lighthouse and installed a light buoy just west of the island in 1948, sea lions and seabirds returned in full force to reclaim their territory. They even moved into the abandoned houses.

Today, the island consists of about seven acres of eroding marine terrace soils and two acres of rocky islets and shifting beaches. The rocks in the intertidal zone are mainly Monterey formation: compacted deposits of clay and silt mixed with skeletal remains of plankton. Interspersed with this silica-rich mudstone is hard black chert once used by the Ohlone for toolmaking. The marine terrace soil above the bedrock on the center of the island is where about 270 rhinos dig their homes.

A hole in the ground does not necessarily mean that someone is home, so researchers use gizmos such as miniature cameras and artificial nest boxes to spy on the rhinos and Cassin’s auklets and document their breeding success. Even after 13 years of banding and measuring rhinos, I still must prepare myself for the physical pain that comes with reaching into the dark nest cavity at the back of a nest box to grab an incubating bird. After being brought into the light, rhinos attempt to free themselves by clamping their thick orange bill onto any nearby finger and swiping their sharp claws at the offending hand.

Females lay one egg between April and May. Both rhino parents share incubation duties. After the chick hatches, they also share feeding duties, each bringing one load of fish or squid to the nest almost every night. After a few late-night explorations outside the burrow, the eight-week-old chicks soon grow their first flight feathers and leave the island, not returning to their natal colony until three to seven years later. What they do in the meantime is a mystery.

Despite their strength, rhinos are easily stressed by human disturbance and often lack the conviction to stick with their breeding investment. If adults are handled more than three times while incubating, they will almost certainly abandon their egg. As for most long-lived seabirds – rhinos live over 20 years – protecting young is not as important as self-preservation from the perspective of maximizing lifetime reproductive output.

To ensure these returning birds find suitable habitat to dig new burrows and look for mates, in 2001 we began testing habitat restoration techniques adapted for the harsh island conditions. With funding from the state Coastal Conservancy and participants from research groups including Oikonos-Ecosystem Knowledge, PRBO Conservation Science, Go Native, and UC Santa Cruz Natural Reserve System, we began getting wet and dirty in earnest in 2003. The main goal was to improve soil stability and increase plant biodiversity in the central marine terrace region. This single acre of habitat has the potential to support more than 500 breeding rhinos. In addition, by revegetating the core of the island, we hope to provide habitat for insects, songbirds, and also local nesting material for all the seabirds.

Restoration experts from Go Native – Dave Sands, Chuck Kozak, and Shawn Dardenelle – designed a unique strategy to stabilize the soil and encourage plant survival. After they planted mature native grasses, spread native seed from the mainland dunes near the elephant seal colony, and covered the seed with straw to provide structure and moisture, the entire island was wrapped in rolls of biodegradable coconut fiber – giving the place the look of a Christo and Jeanne-Claude art installation.

The wrapping strategy is intended to protect the grasses and seeds from the harsh, salty, windy environment long enough for the grass roots to take hold and for the seeds to sprout. As the covering material slowly degrades, it holds moisture and allows plants to grow up through the mesh, creating a lush carpet.

With helicopter support in 2003 and small boats in 2004, we carried more than 30,000 pounds of plants, coconut fiber rolls, seeds, staples, food, and fresh water – for the hardworking crew of volunteers – across the channel. With the help of over 100 volunteers, almost the entire rhino breeding habitat was stabilized in December 2004. Two years of experimenting with plant species and erosion control techniques paid off. Our restoration work reduced erosion and encouraged survival of three native plant species: salt grass (Distichlis spicata), American dune grass (Leymus mollis), and beach bur (Ambrosia chamissonis). In some areas previously completely bare, grasses now cover 30 percent of the area in measured survey grids. This survival and rate of spreading above the erosion control material in only two years exceeded our expectations.

But there have been some surprises. The 10,000 California sea lions that arrived from southern pupping beaches last fall suddenly preferred the center of the island over the edges, beaches, and the surrounding rocky islets. This led to extreme erosion in a portion of the rhino colony. The reason for the sea lions’ behavioral shift will likely never be known, but we should know the consequences for our restoration work in a few months. The slopes we planted in 2003 survived the trampling fairly well; thickly spreading salt grass held the cliffs, and patches of dune grass assisted in trapping moving sand. This spring we will learn how well the less-established plants from 2004 fared.

Future plans include planting successful species in higher densities, experimenting with different plants to increase biodiversity, and documenting the response of the rhinos and other wildlife to the habitat changes over the next ten years or more. With so many species dependent on so little land in such a harsh environment, the island’s ecosystem is sure to change markedly even over a short time. Given the unpredictable and complex dynamics of this island, we can do no more than give the island a “starter kit” that the elements will mold and shape. After the plants are established, we will have to sit back and watch the wind, salt, water, and wildlife create a plant community that might sustain the island’s diverse and abundant life – an abundance so easy to miss from shore and yet so unforgettable to those of us who have made the journey from the mainland.

Click here to download a sound file of the rhinoceros auklet’s call!

About the Author

Ecologist Michelle Hester, president of Oikonos-Ecosystem Knowledge and a research associate with the California Academy of Sciences, has studied seabirds and island ecology in California, the Caribbean, and Antarctica.