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by Nanea Kalani, ‘06

 

A native Hawaiian bird that was once the most abundant native land bird on O‘ahu is now an endangered species, threatened most by human damage to its habitat, according to Ken Foote, an external affairs specialist for the U.S. Fish and Wildlife Service’s Pacific Islands region.

The O‘ahu ‘elepaio, a small forest bird found only on the island of O‘ahu, was placed on the list of endangered species by the wildlife service in May 2000.

The bird is a member of the monarch flycatcher family and about the size of a wren. Adult birds have dark brown heads, backs, and tails with white underparts, with light brown streaks on the upper breast. They often hold their long tails up at an angle. ‘Elepaio don’t migrate off of O‘ahu, often mate for life, and are insectivorous, meaning that they only eat insects.

But humans have gotten in the ‘elepaio’s way: Clearing forests for homes, buildings and crops has caused much of the decline in the species’ population, resulting in poor reproduction and low adult survival, Foote explained.

About 2,000 ‘elepaio now live on O‘ahu, which is less than 4 percent of its original population of about 50,000.

Rats, which prey on ‘elepaio nests, also have cut the species’ survival rate. And mosquitoes carrying diseases such as avian pox and malaria infect about 14 percent of the species’ population each year. No effective and environmentally safe method of controlling mosquitoes in forested habitats exists, according to the Web site of the Hawai‘i Department of Land and Natural Resources Division of Forestry and Wildlife.

While forest birds make up the largest group of native Hawaiian birds, with 60 species and subspecies statewide, the forest bird group also has lost the most species, including 22 that are extinct and 23 that are endangered in Hawai‘i, according to USFWS.

In 2001, the wildlife service designated more than 65,000 acres of critical habitat on O‘ahu to help revive the O‘ahu ‘elepaio population and remove it from the endangered list.

Five critical habitat units have been designated for the O‘ahu ‘elepaio, including “most of the area currently occupied by the bird, plus some unoccupied historical habitat (areas that the species formerly occupied) to provide for a self-sustaining population,” said Foote. “Past surveys document the average-size territory that an ‘elepaio pair requires and, based on that, the critical habitat areas would be able to support a population of about 10,000 birds.”

Because ‘elepaio are highly territorial and each pair defends a territory of a certain size, the areas occupied by the species before the designation were too small to support a healthy population, said Anne Badgley, regional director for the wildlife service’s Pacific Islands region, in a June 6, 2001, USFWS news release.

“Therefore, we added unoccupied lands containing the elements needed by ‘elepaio which will allow existing populations to expand, and help link subpopulations by encouraging genetic exchange as single birds move from one area to another,” she said in the release.

The five areas include more than 46,000 acres in the central and southern Ko‘olau Mountains, approximately 17,000 acres in the northern and southern Wai‘anae Mountains and nearly 2,000 acres in Kalihi-Kapalama.

As of 2005, the Fish and Wildlife Service estimates that 26 to 50 percent recovery has been achieved for the O‘ahu ‘elepaio, said Foote. “The likelihood of the species being completely removed from the list [of endangered species] is low,” he said.

The Hawai‘i State Division of Forestry and Wildlife used snap traps, bait stations, and other ground-based rodent control methods from 1996 to 2000, resulting in average increases in ‘elepaio reproduction of 112 percent and female survival by 66 percent, according to a study published in the 2002 issue of Pacific Conservation Biology.

These ground-based methods, however, are labor intensive and cover limited areas. Large-scale methods are needed to further increase the endangered species’ population, according to the Hawai‘i State Division of Forestry and Wildlife, which recommends implementing aerial broadcasting of bait.
Because many of Hawai‘i’s native forest birds live in steep valleys, it’s difficult to manually place rat traps there. But aerial broadcasting by helicopter would deliver bait that is suitable in size and shape for precise distribution to remote areas.

Despite public health concerns, aerial broadcasting of rodenticides has had substantial success in New Zealand, and local scientists recognize the method’s potential. “Initially, I cringed at the idea of dropping toxicants from the sky,” said Trent Malcolm of the Maui Forest Bird Recovery project in the August 2003 issue of BioScience. “But it’s important to remember that not all toxicants behave the same in the environment. The benefits of aerial broadcasting in Hawai‘i’s native forest could be enormous [because] if we lose just one bird to predation, the species could be doomed to extinction.”

Future looks bright for endangered native bird.

 

 

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