One of the mantras of conservation is that a tiny population in a single location is inherently at risk.
That’s why conservation agencies are working this week to establish a population on Laysan Island of the Nihoa millerbird.
(Image: Nihoa millerbird, which will help create a new population of millerbirds on Laysan. Credit: Robby Kohley via U.S. Fish and Wildlife Service.)
This has been done before with another single-island species from Nihoa, the Nihoa finch, which now has a backup population on Pearl and Hermes Atoll. And it’s been done with the Laysan duck or teal, which now also exists on Midway Atoll.
The new transfer is a joint effort of the U .S. Fish and Wildlife Service and the American Bird Conservancy, with the help off the group Pacific Rim Conservation. All the islands are within the Papahānaumokuākea Marine National Monument, which covers the islands, reefs, seamounts and atolls of the remote northwestern end of the Hawaiian archipelago.
A team working from the motor vessel Searcher is on Nihoa this week, seeking to collect 24 millerbirds for the transfer. Millerbirds have previously existed on Laysan, but not for nearly a century. The birds will be taken aboard the ship, which will power to the northwest to Laysan, a 650-mile voyage.
The two islands had different varieties of the the millerbird. The one on Laysan was Acrocephalus familiaris familiaris and the one on Nihoa is Acrocephalus familiaris kingi. They were very similar. Laysan’s millerbird went extinct during a period when introduced rabbits destroyed virtually all green vegetation on Laysan Island. The rabbits were eventually eradicated, and some of the original vegetation is back now.
The insect-eaters are active gray-brown birds that forage among low shrubbery on Nihoa. What are the risks for them? Nihoa is a tiny rock island, and fire, rats, disease-carrying mosquitoes, storm or any number of threats could wipe them out. Even rabbits.
The world expert on millerbirds is University of Hawai’i zoologist Sheila Conant, who studied them extensively in the 1980s and has watched the population whipsaw from as many as 800 birds to as few as 30. She is a strong proponent of translocation.
“For thousands of years, the Nihoa Millerbird miraculously survived low numbers, catastrophes including a severe brush fire in the late 1800s, and, most importantly, existence on a single tiny island.
"These threats are as serious today as they have ever been, and are compounded by the potential for non-native predators and diseases to be introduced to Nihoa. This translocation could more than double the total number of birds by establishing a second population on another island, and provide insurance for the species,” Conant said.
Read more about the millerbirds at the American Bird Conservancy site.
© Jan TenBruggencate 2011