Thanks to painstaking dune restoration, the wedge-tailed shearwater has returned to TNC's Mo‘omomi Preserve in Hawai‘i.
It was dusk the first time Jay Penniman took in the full scope of the seabird colony taking hold at Mo‘omomi. It was 2007, and Penniman and a team of volunteers in pickup trucks had bumped along the dirt road to the shore, through a stand of invasive kiawe trees so thick they seemed to form a tunnel. As the group rounded a corner, the trees suddenly parted, revealing a sky awash in pinks and purples and a landscape of gently rolling sand dunes, carpeted in creeping vines and soft grasses.
Penniman, manager of the Maui Nui Seabird Recovery Project, had arrived to count and band adult wedge-tailed shearwaters in The Nature Conservancy’s Mo‘omomi Preserve. The preserve sits on the remote northwestern shore of Moloka‘i, one of Hawai‘i’s most sparsely populated islands, separated by less than 9 miles of water from touristy Maui.
The seabirds, once numerous throughout the Hawaiian Islands, had all but disappeared from Hawai‘i’s larger islands—including Moloka‘i—centuries ago, making their colonies instead on tiny, uninhabited islets offshore, where they were safe from cats and other predators. But in 1999, a wedge-tailed shearwater nest was discovered in the dunes at Mo‘omomi. Since then, as staff and workers gradually removed kiawe thickets in an effort to restore the dunes, the bird’s population had steadily grown.
As the team got out of their vehicles, a flash of movement caught Penniman’s eye. A seabird, its white belly round from a long day of fishing, glided in over the darkening waves, effortlessly skimming over a large dune before lifting briefly, pivoting on the wind and dropping down to land out of sight.
Penniman had visited Mo‘omomi once before to count chicks during the day; they hide in their burrows while their parents feed at sea. But this was the first time he was seeing it come to life at night, when the adults return to their nests.
As his eyes adjusted to the deepening twilight, Penniman realized he could see dozens of the birds making landfall—a rare sight in the main Hawaiian Islands. All around him, shearwaters waddled awkwardly toward the mouths of their underground burrows. Then the air began to fill with haunting cries, almost like babies’, of birds calling for their mates.
Listening to the mass of shearwaters alighting around him, he realized that he was witnessing a shift in the centuries-long trend of the bird’s decline. “It was like stepping back in time to ancient Hawai‘i, before the invasion of non-native species,” Penniman says. “It was stunning for me. … Restoration really can happen.”
The wedge-tailed shearwaters are not just visitors. They helped kick-start the islands’ ancient ecosystem. According to Penniman, seabird droppings brought nutrients from the ocean to enrich the sandy and volcanic Hawaiian landscapes—a process that, over millennia, helped build soil and an environment that could support a rich diversity of plant and animal life.
Grayish brown, with watchful black eyes and a long, hooked beak, the birds have graceful wings that open to a span of around 3 feet—more than twice their body length. The birds from Hawai‘i are predominantly white-breasted.
Ancient Polynesians followed shearwaters and other seabirds as part of their navigational tool kit to help find the Hawaiian Islands as they explored the Pacific Ocean. Wedge-tailed shearwaters—known in Hawaiian as ‘ua‘u kani, or “moaning petrels,” for their wailing call—have long guided fishermen to schools of skipjack tuna. “The fishermen knew that a feeding flock of seabirds would be over the area where big predator fish pushed the bait fish to the surface,” Penniman says.
Wedge-tailed shearwaters and other seabirds were once so abundant on the coasts of the Hawaiian Islands they were said to darken the sky. The arrival of Polynesian settlers in the islands started their decline; early Hawaiians took them for food and brought the first mammalian predators—rats, dogs and pigs. After Westerners arrived in the late 1700s and introduced cats, the birds’ population plummeted.
Since they spend most of their lives flying at sea, there is still a lot to learn about the wedge-tailed shearwaters, but what scientists do know about them is pretty fascinating, Penniman says. They can swim about 90 feet underwater to catch fish. In the air, the birds barely flap their wings, soaring for hours on the winds. They spend December to March living at sea, covering a range scientists believe could be thousands of miles, returning to land every March to mate and nest. Banding and tracking events like those Penniman has led with TNC at Mo‘omomi Preserve have shown that wedge-tailed shearwaters prefer to return to the same colony where they hatched—often reusing the same burrows to nest each year.
Shearwaters are monogamous, and greet each other tenderly when reunited, preening each other and cooing before retreating to the privacy of their burrow to mate. As long as both birds survive and successfully breed, the pair will raise a single chick each year that may live more than 20 years. Although mother and father take turns incubating their egg, within a few days of hatching the chick is left alone during the day so both parents can fish.
But habitat loss and the fact that the birds evolved without terrestrial predators are some of the reasons why these shearwaters have struggled to survive in modern Hawai‘i.
Mo‘omomi Preserve had long been shortlisted for preservation by TNC, not only because it represented one of the largest and last coastal dune ecosystems in Hawai‘i, but also because it was known to be rich in cultural and natural resources. The Conservancy had an opportunity to acquire the property from the former Moloka‘i Ranch in 1988. The 921-acre property held the most expansive intact coastal dune ecosystems in the main Hawaiian Islands—a habitat that was largely lost to development on the bigger islands. Mo‘omomi still had an open landscape, but the dunes had been invaded by invasive plants, especially the kiawe, a thorny mesquite tree that was crowding out native vegetation and preventing wedge-tailed shearwaters from nesting.
The shearwaters weren’t on the radar yet, says Ed Misaki, TNC’s director of programs on Moloka‘i. The goal at Mo‘omomi has always been to preserve the dunes and restore the coastal ecosystem, which includes low-lying native grasses and shrubs that have largely been lost in more developed parts of the islands.
The kiawe trees, which grow 6 to 25 feet tall at the preserve, are so thick and dense that local crews hired by TNC must work from the outside in to remove them, cutting back the outer branches until they reach the trunk, says Misaki, who has worked for the organization for 35 years. The stump is treated to prevent regrowth, and the branches are shredded in a wood chipper. The mulch is spread across the area to stabilize the bare ground until native plants can take hold.
As crews cleared the area of the trees, ‘aki‘aki, a low-lying native grass, began creeping back in, blocking out invasive plants and setting the stage for other native species to regrow. Misaki refers to Mo‘omomi’s management strategy as “passive restoration”—giving natives room to recover and letting them move in, versus trying to replant everything. Native dune habitats would gradually rebuild themselves when given relief from the invasives. “Nature is really telling you what to do,” he says.
In 1999, less than 10 years after TNC began restoring the preserve, the first shearwater nest at Mo‘omomi was discovered. Misaki said he was surprised; it was the first time seabirds had been found nesting in the preserve. “That was an exciting moment,” he says. “Wow, the birds want to nest here.” Almost immediately, a protection plan was developed to determine threats to the birds. A year later, there were 20 nests. Workers continued clearing more kiawe. The year after that there were 75 nests.
But as the nesting wedge-tailed shearwater population grew, the staff saw signs of mortality among the birds. Adults and chicks were being killed by feral cats, stray dogs and mongooses—all non-native species. Predator control has been part of the preserve’s restoration plan since the first nest was found.
Conservancy staff also realized that axis deer—another invasive species—were part of the problem as well. As the deer ate native plants near the wedge-tailed shearwaters’ nesting sites, they trampled the fragile dunes, causing the burrows to collapse, burying the birds alive. In 2006, TNC installed a 1.5-mile fence near the dune. It was designed to keep predators and deer out of the nesting area, and withstand the salt air and coastal wind.
Removing more kiawe helped reduce the effectiveness of predators, too. Workers pulling out the tangled, thorny trees in one stand found piles of wings underneath. Cats had been using the trees as cover to stalk the seabirds, then returning to their hideouts to eat their kill. “When we removed the kiawe, we gave the feral cats less habitat to attack the birds from,” says Russell Kallstrom, TNC’s Moloka‘i field information coordinator and a native of the island.
By the time Penniman led his first banding effort in 2007, Mo‘omomi Preserve hosted hundreds of nests. And by 2009, clusters of them were visible on Google Earth. “We [could] see our work from space,” says Kallstrom. “We were really making a difference.”
Volunteers Help With Bird Banding
“Today we’re up to almost 2,000 nests,” says Misaki. With results like that, he adds, “it’s an indication you must be doing something right.” So far, more than 12 acres of the tenacious kiawe have been removed. The yearly surveys and bandings have proven that much of the early wedge-tailed shearwater population growth was coming from colonies on offshore islets that were at maximum capacity.
By checking the birds’ bands, scientists know that the preserve has developed its own native population of wedge-tailed shearwaters. As many as 95 percent of the birds nesting at Mo‘omomi today were born and raised there.
And in the 20 years since that first nest was spotted at Mo‘omomi, other landowners in the surrounding area have begun removing invasive plants and animals.
It has been a remarkable transformation for a remarkable piece of land, says Kallstrom. He calls Mo‘omomi “one of the last and best remaining coastal dune ecosystems in the main Hawaiian Islands, and one of the largest as well.”
In addition to its ecological importance, the area has long been a place of cultural significance to the Native Hawaiian community, he notes. For centuries, local families have harvested the area’s fish, shellfish and seaweed, and collected basalt rocks to make woodworking tools. Mo‘omomi also contains many ancient burial sites. “It’s a very sacred area where kūpuna [ancestors] have been laid to rest,” he says. “To be able to maintain the area and actually bring it back is a real honor.”
As the team assembles at Mo‘omomi for another banding, they gather in a circle before fanning out across the dunes. Kallstrom steps forward and raises his voice. “Kūpa‘a kumuone Kaiehu i ke Kuapā,” he begins, reciting a Hawaiian oli, or chant, that was written for the occasion by Sam ‘Ohukani‘ōhi‘a Gon, TNC’s senior science and culture adviser for Hawai‘i. The chant invokes Mo‘omomi’s sandstone and wind, the sea spray and the roots of the naupaka shrub, where ‘ua‘u kani brood. It also announces the arrival of the group as kahu, or caretakers, who seek to enter the area with a humble spirit.
“Part of it is simply acknowledging why we’re there,” Kallstrom says. “So to me, this oli has almost become like a vision statement, putting into words what we are there for, and what we would like to see.”