Millerbirds Return to Laysan Island After 100-Year Absence

By Ken Foote

The sun beats down on a small rocky island in the middle of the Pacific Ocean. A lively brown song bird that weighs less than an ounce forages for insects among the low shrubs and bunch-grass. This nondescript bird is known as the Nihoa Millerbird (Acrocephalus familiaris kingi), and it is barely noticeable among the seabirds, insects, and other animal and plant species that inhabit the island.

The first fledgling Millerbird produced on Laysan in March 2012. Photo Credit: R. Kohley / American Bird Conservancy

The first fledgling Millerbird produced on Laysan in March 2012.
Photo Credit: R. Kohley / American Bird Conservancy

This extremely rare bird was one of the first bird species to be listed as endangered in 1967—preceding the present-day Endangered Species Act by six years. Until recently, the bird was found only on Nihoa Island. Nihoa Island is a rugged 155-acre (63-hectare) volcanic island, one of the many islands and atolls that make up the Northwestern Hawaiian Islands – part of the Papahānaumokuakea Marine National Monument – stretching 1,200 miles (1,900 kilometers) northwest from the island of Kaua’i.

Historically, there were two populations of Millerbirds, one on Laysan Island and one on Nihoa Island. The Laysan Millerbird (Acrocephalus familiaris familiaris), along with the Laysan Rail (Porzana palmeri) and Laysan Honeycreeper (Himatione sanguinea freethi), went extinct in the early 20th Century when the island was denuded by non-native rabbits and livestock. Thus, the Millerbirds on Nihoa were the only Millerbirds remaining anywhere on Earth.

Millerbird numbers on Nihoa fluctuate between 30 and 800 birds. This single, small population faces a high risk of extinction from catastrophes such as severe storms, droughts, fires, or accidental introduction of alien species such as rats, mosquitoes, and diseases such as avian pox and malaria. Establishing a second population on the 1,023-acre (415-ha) Laysan Island will reduce this risk by increasing the total population size and the distribution of the species.

Treacherous transfer of Millerbirds from Nihoa to zodiac during the 2012 translocation. Photo Credit: Ryan Hagerty / USFWS

Treacherous transfer of Millerbirds from Nihoa to zodiac during the 2012 translocation.
Photo Credit: Ryan Hagerty / USFWS

In 2011 and 2012, a team of dedicated scientists and volunteers undertook a monumental task of capturing and translocating, or moving, 50 Millerbirds. The birds were moved an incredible 650 miles (1,046 km), by sea, from Nihoa to Laysan Island. Two separate translocations were conducted; 24 birds were moved in 2011, and 26 in 2012 with scientists trying to maintain an equal sex ratio of males to females.

The release was the result of many years of research and detailed planning by biologists and resource managers, led by a partnership between the U.S. Fish and Wildlife Service and American Bird Conservancy. The successful translocations mark the first time in nearly a century that Millerbirds have occupied Laysan Island. Today, we estimate over 38 fledglings have been produced on Laysan. The total island population is estimated to be over 63, and biologists are working to get a more exact count over the next few months.

As a co-manager of the Papahānaumokuakea Marine National Monument, the U.S. Fish and Wildlife Service is proud to lead this project in collaboration with the American Bird Conservancy. The National Fish and Wildlife Foundation, the University of New Brunswick, University of Hawai’i, Pacific Rim Conservation, Pacific Bird Conservation, the U.S. Geological Survey National Wildlife Health Research Center, and the Office of Hawaiian Affairs have also supported this effort.

Ken Foote, an information and education specialist in the Service’s Pacific Islands Fish and Wildlife Office, can be reached at ken_foote@fws.gov

Learn more about the translocation effort.

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