Predator-Proof Fence Saves Seabirds in Hawaii

This Newell's shearwater chick, a threatened species found only in Hawaii, is one of several seabirds recently moved to a predator-proof habitat at Kilauea Point National Wildlife Refuge, Kauai. (Photo: André Raine/Kauai Endangered Seabird Recovery Project)

The Newell's shearwater is one of two seabirds endemic to Hawaii, meaning it exists nowhere else on Earth. The species nearly stopped existing even in Hawaii, driven to the brink of extinction by invasive species, habitat loss and light pollution.

Now, however, the outlook may be brightening for the Newell's shearwater — known as 'a'o in Hawaiian — thanks to a rehab project on the island of Kauai.

Newell's shearwaters once thrived on all the main Hawaiian islands, but after decades of decline, they were added to the U.S. endangered species list in 1975. Today they're mostly limited to Kauai, where about 90 percent of all survivors live. Because they're threatened by invasive predators like cats and rats, several young chicks were recently relocated to the island's first "predator-proof" sanctuary, a 7-acre native habitat encircled by more than 2,000 feet of 6-foot-high fencing.

Nihoku Predator Fence Project
A view of the Nihoku predator fence with Mōkōlea Point in the background. The fence uses mesh small enough to keep out baby mice, park officials say, and has a hood to prevent predators from climbing over. (Photo: U.S. Fish and Wildlife Service)

And now, to the relief of conservationists, a few of those chicks have finally begun to fledge. Here's one of the first fledglings as he works out his wings:

Newells Shearwaterwe are excited to report that the first translocated Newell's Shearwater chick has fledged from Kilauea Point National Wildlife Refuge! He worked hard for almost a week exercising those wings. With Kaua'i Endangered Seabird Recovery Project, American Bird Conservancy, U.S. Fish and Wildlife Service, Hawaii DLNR (Department of Land and Natural Resources), and National Tropical Botanical Garden.
Posted by Pacific Rim Conservation on Thursday, October 6, 2016

"It really makes me happy to see them out there flapping and practicing, and then to have them fledge like normal birds," Robby Kohley, an avian ecologist with Pacific Rim Conservation (PRC), tells Jessica Else of The Garden Island newspaper.

Like many Hawaiian birds, the Newell's shearwater has been obliterated over the past century by non-native predators that prey on eggs and chicks. It evolved in Hawaii with few natural enemies, allowing it to nest safely in underground burrows, often around the roots of trees. But when people began introducing cats, rats, dogs and mongooses to Hawaii, these once-safe nests suddenly became easy pickings.

Mending fences

cat predation of Hawaiian seabirds
Cats still pose a major threat to many Hawaiian seabirds. In this photo, a camera trap catches a cat pulling an endangered Hawaiian petrel chick from its nest. (Photo: Kauai Endangered Seabird Recovery Project/Facebook)

Wildlife refuges can protect important habitats for seabirds, but cats and rats don't recognize refuge boundaries like humans do. To keep seabird chicks safe from those exotic predators, conservationists have begun to fence off nesting habitats in some parts of Hawaii. This has benefitted species like the endangered nene goose on Oahu, for example, and now the strategy is being tested on Kauai.

Located at Kilauea Point National Wildlife Refuge (KPNWR), the fence protects seven acres of native coastal habitat in an area known as Nihoku. It was completed in September 2014, and after a trapping campaign, all invasive predators were removed from the fenced section a few months later. The U.S. Fish and Wildlife Service (FWS), along with several conservation groups, began restoring native plants and installing seabird-friendly nest boxes, which are designed to mimic natural burrows.

Cats and rats are both notoriously good at accessing forbidden places, but according to KPNWR ranger Jennifer Waipa, this fence is specially designed to keep out even the smallest or nimblest threat to young seabirds. "The mesh is so small that even 2-day-old mice can't get in, and the fence is buried into the ground," Waipa tells Else. "And there's a hood over the top of the fence so nothing can climb over."

Nihoku Predator Fence Project
The Nihoku predator fence, pictured here during construction in 2014, features a sloped hood along the top to stop animals from climbing into the protected area. (Photo: Jesse Behnke/FWS)

Invasive species aren't the only threat to Newell's shearwaters, though. Like baby sea turtles, young shearwaters are instinctively attracted to light, which guides fledglings on their first flight out to sea from their nesting grounds. Urbanization in recent decades has brought more electrical lighting to remote parts of Hawaii, which has resulted in "substantial problems" for Newell's shearwaters, according to the FWS.

"When attracted to manmade lights, fledglings become confused and often fly into utility wires, poles, trees and buildings, and fall to the ground," the agency explains. "Between 1978 and 2007, more than 30,000 Newell's shearwaters were picked up by island residents from Kauai's highways, athletic fields and hotel grounds."

The Nihoku predator fence can't protect the fledglings from every danger, but its location at KPNWR does offer them a safe space relatively far from the confusing glow of more urban areas. And by protecting the chicks from exotic predators, it at least helps more of them have a chance to fledge in the first place.

No place like home

Nihoku Predator Fence Project
A double rainbow gleams over the finished predator fence at Nihoku. (Photo: FWS)

Some seabirds already nested in the protected area, the FWS notes, including nenes and Laysan albatrosses. In 2015, conservationists also began introducing endangered Hawaiian petrel chicks, hoping to create "a new, predator-free colony" to buffer that species on Kauai. And in mid-September 2016, the Nihoku Predator Fence Project expanded again with the addition of eight Newell's shearwater chicks.

Those chicks were walking around outside their burrows by late September, and after the first one fledged in early October, PRC announced two more had fledged on Oct. 13. Once they fledge, the birds will remain at sea for three to five years — but if everything goes as planned, they'll never forget where they came from.

Newell's shearwater chicks imprint on the location of their birth colony the first time they emerge from their burrows and see the night sky, according to the Kauai Endangered Seabird Recovery Project (KESRP). And since these eight chicks were relocated to Nihoku before they had reached this critical imprinting stage, conservationists hope they've imprinted on this part of Kauai as their birthplace. If so, they'll eventually come back as adults to have babies of their own.

"Kauai is home to an estimated 90 percent of the world population of Newell's Shearwater, so the island really is critical to the long-term survival of this species," André Raine of KESRP says in a statement. "Now is the time to focus all of our efforts on protecting the remaining colonies, using all the management strategies available to us, and establishing new colonies in protected areas like Nihoku. By using a diverse array of approaches, we hope to ensure that these beautiful birds will continue to grace our islands long into the future."