For the first time in four years, Newell’s shearwaters have started laying eggs in an artificially created seabird colony in West Maui.
Biologists confirmed that four human-made burrow boxes – three with eggs – are being occupied by the threatened species this season. According to the biologists, that’s “right on schedule.”
“It was kind of a risk setting up the enclosure at all, because this method hadn’t been tried before (in Hawaii),” project biologist Matt Stelmach said Tuesday. “When I first heard about the project, I wasn’t involved. I was skeptical. . . . And, now that I’m involved, I’m really excited to see that it’s becoming a success, because it has the potential to change management practices across Hawaii, at least for seabirds.”
The two 4.5-acre, predator-free enclosures were constructed near the Makamakaole Stream basin in 2012 and 2013 to offset accidental deaths of native seabirds at the Kaheawa wind energy facilities above Maalaea.
Scientists have tried to create new colonies of birds before, sometimes by transporting the creatures to new locations.
“But here in Hawaii, we’ve never tried to do acoustic attraction, which is the unique aspect of this restoration effort,” Stelmach said.
Every night, seabird social calls similar to those at existing colonies were broadcast through weatherproof, solar-powered sound systems, according to an announcement from TerraForm Power, owners of the Kaheawa wind facilities. Within the enclosures, biologists have installed 100 “burrow boxes.” The corrugated plastic burrows connect to underground plywood boxes that serve as nesting chambers, mimicking the birds’ own natural habitats. A 6-foot-high mesh fence protects the enclosures, and “year-round intensive predator control” keeps the area clear of predators.
The goal was to attract the shearwater and the endangered Hawaiian petrel to an area where both species had been assumed absent for more than a decade.
“We’ve known that the Hawaiian petrel has nested in the nearby Makamakaole drainage areas, but they’re unprotected from cats, rats, mongoose,” said Fern Duvall, head of Maui’s Native Ecosystem Protection and Management Program with the state Department of Land and Natural Resources. “They’ve slowly disappeared. The only places in West Maui that they’re nesting in now that seem to be fairly safe from those things are vertical cliffs in very remote areas.”
The results in the Maui enclosures match similar tests in New Zealand, where the first signs of nesting activity usually occurred three to four years after the colonies were established.
Biologists suspect that some young birds may be getting displaced from an existing colony in West Maui, Stelmach explained. Something may be keeping them from nesting in that colony, so they’ve set out in search of a new home – and found the predator-free enclosures.
“As the colony gets larger and larger, it creates more attraction,” Stelmach said. “The likelihood is that as time goes on, the colony will draw in more seabirds, and we’ll be able to create a colony using social attraction.”
Because these birds are the first to start making the colony home, biologists are being cautious. They’ve set up game cameras so they can watch from afar. They don’t plan to go in and put bands on the initial birds because it might disrupt the colonization.
However, if chicks hatch, biologists might band those while adults are away feeding during the day, Stelmach said. He explained that when the chicks emerge from their burrows for the first time, they “imprint on the stars” and are then “attached to that location. So the chicks are much less sensitive to disturbance.”
Meanwhile, Hawaiian petrels have also shown interest but have yet to nest. Stelmach didn’t want to speculate on what’s keeping them from settling down, but he added that nesting was expected four to five years after the enclosures were created. The whole project will be evaluated after next year’s nesting season, which runs from March to November.
Duvall and Stelmach said success at the Makamakaole enclosures could open the door to more predator-proof habitats around Hawaii. While translocating birds has worked in the past, it takes up a lot of resources, Stelmach said. Chicks have to be constantly monitored and carefully moved before they imprint on one location.
The West Maui enclosures are among several projects that TerraForm is required to implement to offset bird deaths at its wind farms. Kaheawa Wind Power I and II include 34 wind turbine generators ascending the West Maui slopes. Both sites have 20-year, state-issued licenses that place a limit on incidental bird deaths.
An estimated 16 petrels have been killed at the Kaheawa I site since it was permitted in 2006, and none at Kaheawa II since it was permitted in 2012, said Mitchell Craig, TerraForm’s compliance manager for its Habitat Conservation Plan. Biologists have not recorded any Newell’s shearwaters killed at either site. The total estimated take over the 20-year period is 31 petrels and zero shearwaters at Kaheawa I, and neither petrels nor shearwaters at Kaheawa II.
Craig said the enclosure in West Maui aims to replace 53 petrels and 16 shearwaters.
“Population modeling for the Makamakaole mitigation site suggests it would take 20 to 30 years to replace that many petrels, and five to 10 years to replace that many shearwaters,” Craig said. “It would take considerably less if the colony grows faster than expected.”
Duvall said the mitigation plans are scrutinized by an Endangered Species Recovery Committee made up of representatives of federal and state agencies, including the DLNR. Every plan has to offer “a net benefit to the species.”
“I do think that in this case, getting the birds to breed in a new location and producing young in a safe area, they’re well along the road to having a very successful mitigation,” Duvall said.