Pacific Islands Fish and Wildlife Office
Pacific Region

Endangered Species in the Pacific Islands

Nihoa Millerbird / Acrocephalus familiaris kingi

Photo of Nihoa millerbird The Nihoa millerbird is a tiny land bird measuring approximately 5 inches in length that was discovered on the island of Nihoa in 1923. Another subspecies once occurred on Laysan Island, where it went extinct in the early 20th century after the island was devegetated by introduced rabbits. It has dark gray-brown feathers above, a buffy-white belly, and a thin dark colored bill. This bird got its name because its favorite food is the miller moth. Male and female birds are similar looking.
Nihoa millerbird - Photo credit Craig Rowland/USFWS

Habitat & Behavior:
The Nihoa millerbird is found only on Nihoa and because Nihoa is a mere 156 acres, its habitat is very limited.

These shy little birds spend their time near the ground in goosefoot (Chenopodium sanwicheum) and ilima (Sida Fallax), where they forage for insects. Their nests are constructed of grass stems and rootlets and concealed in small shrubs. Nesting may occur anytime between January and May, and an average of two eggs are laid.

The millerbird has a metallic and bubbling voice, but it is not easily heard because of the terns flying overhead and the pounding surf below.

Past & Present:
The population size of the Nihoa millerbird has fluctuated between 300 and 700 birds in the last 30 years. The 2009 population estimate was 641 plus or minus 295 Nihoa millerbirds. Threats to the millerbird include small population size, limited distribution, introduced plants and animals, and fire. All these threats are very serious as this is the only place in the world where these birds can be found.

Conservation Efforts:
The Nihoa millerbird was listed as an endangered species in 1967 under the Federal Endangered Species Act. Nihoa is part of the Hawaiian Islands National Wildlife Refuge created in 1909 and the Papahānaumokuākea Marine National Monument, and access is restricted due to the island’s fragile ecosystem. It is also designated as a Research Natural Area where state and federal biologists work closely together to monitor and maintain Nihoa’s wildlife and environment. Biologists are considering the translocation of sufficient millerbirds to create a second population on another Hawaiian island to reduce the risk of extinction. A ranking of potential translocation sites for the millerbird indicated that Laysan Island is the first choice for a translocation effort. Planning is underway for this project.


Last updated: September 20, 2012
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