Molokaʻi Shearwater Colony Now One of State’s Largest
Colony has grown from two nests in 1999 to almost 1,500 today
HONOLULU, HI | December 04, 2017
In 1999, two wedge-tailed shearwater nests were discovered at The Nature Conservancy’s Moʻomomi Preserve on Molokaʻi. Today, the coastal preserve is home to one of the largest and best protected shearwater colonies in the state, with almost 1,500 active nests and over 3,200 birds.
It’s a remarkable success story that was achieved by clearing acres of invasive weeds and controlling the predatory animals that threaten the shearwaters’ survival. The colonization has been dramatic, and it’s been tracked by annual bandings of the nesting adults and their chicks.
“The fact that the wedgetails are returning to Moʻomomi tells us that the area is really healthy. Because the ecosystem is healthy, the species that are supposed to be there are returning,” said Wailana Moses, the Conservancy shearwater coordinator.
The Nature Conservancy’s 923-acre Moʻomomi Preserve is a last stronghold of a coastal dune ecosystem that has almost disappeared from the main Hawaiian Islands. The preserve protects almost two dozen native coastal plant species, including four that are endangered. It is an important nesting site for the green sea turtle and was once home to at least 30 bird species, about one-third of which are now extinct.
When the Conservancy acquired Moʻomomi in 1988, there were no shearwaters. Although the birds are not endangered, shoreline development and predation have driven them from their coastal homes to the safety of offshore islets. When two shearwater nests were found at Moʻomomi in 1999, it marked the first time in decades.
“We were excited, of course, and the following year we went out there and found 20 nests,” says Ed Misaki, the Conservancy’s Molokaʻi program director. “That’s when we decided we should start managing for the shearwaters because they were trying to establish a colony.”
The challenges were significant. A dense Axis deer population trampled nests and ate the coastal vegetation whose roots supported burrows in the sand. Loose dogs killed shearwaters in massive numbers—in one night 70 were killed by a single dog. Cats were using kiawe thickets as refuges where they brought dead birds to eat them. Mongooses and rats were additional threats.
The Conservancy launched predator control programs, pushed back the thorny kiawe to create 19 acres of new habitat, and built a 1.5-mile coastal fence to keep the animals from returning. The result is a Moʻomomi whose native residents—including birds and plants—are thriving.
“Moʻomomi is a very significant colony for the state—it’s now among the largest populations,” says Jay Penniman, project manager of the Maui Nui Seabird Recovery Project. “It’s a shining example of what you can do by just changing the habitat and removing predators—it’s a jewel.”
Nest counts at Moʻomomi have been ongoing since 2000, with the banding beginning in 2005. Led by Penniman and State wildlife biologist Fern Duvall, the bandings take place twice a year.
Banding of adult birds occurs one night every spring, when the shearwaters return to prepare for the nesting season and to look for or reunite with a mate. Each band is numbered, and data is entered into an international database to track species demographics. In the fall, volunteers return to monitor nesting activity. Then, in late October, they go back to band the shearwater chicks. This October, volunteers banded 239 news chicks.
“The main purpose of the banding is to find out more about these birds so that we can protect them better,” Moses said.
Wedge-tailed shearwaters — or ‘ua‘u kani — are large, dark-brown migratory birds with a black-tipped dark-gray bill. The birds live all their lives at sea and come ashore only to breed, returning to the same nest site each year. Their annual return benefits the preserve because their droppings bring important marine nutrients back to the land. Plants become far more vigorous, reinstating ecosystem function that has been lost.
Local fishermen know wedge-tailed shearwaters as the “aku” bird. Out at sea, schools of akule feed on large schools of bait fish and drive them to surface. When fishermen see the wedge-tails feeding on the bait fish they know there are akule below.
The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world's toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. Working in 72 countries, we use a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit www.nature.org or follow @nature_press on Twitter.