U.S. Department of the Interior USGS FS 2006-3013

U.S. Geological Survey February 2006

An endangered native avifauna

The forest birds of the Hawaiian Islands are distinguished by 

the diversity of endemic forms derived from a small number of 

ancestral colonists. However, the avifauna has been decimated 

by human activities both before and after Western contact. At 

least 71 species or subspecies disappeared before the arrival of 

Capt. James Cook in 1778, and an additional 24 went extinct 

after 1778, of which 11 were lost since the 1960s alone. Many 

of the remaining Hawaiian bird populations are declining or are 

in danger of extinction. Vigorous efforts to survey and monitor 

bird populations over the past 3 decades have generated considerable information from which to assess the current status of the 

Hawaiian forest birds.

Management of forest birds and their habitat is driven by 

such questions as:

• How large is a species’ population?

• How are birds distributed across the landscape, and where 

are the populations concentrated?

• What proportion of populations lie within and outside protected areas? 

• What habitat associations are favored by native and endangered species?

• Have past restoration projects resulted in increases in native 

and endangered bird numbers? What conservation practices 

will benefit bird species in the future?

• How can bird surveys be improved to better predict distributions and track population numbers? 

• How might human activities and climate change affect the 

distribution of bird populations?

Synthesizing over 30 years of survey data

In collaboration with a broad group of partners (see next 

section), scientists at the USGS Pacific Island Ecosystems 

Research Center have developed the Hawai‘i Forest Bird Interagency Database Project (HFBIDP) to integrate the wealth of 

information generated from forest bird surveys conducted since 

the mid-1970s on the major Hawaiian Islands. The information 

is being used by the HFBIDP to assess species status and to develop statistical models for predicting and mapping the association of bird abundance with habitat attributes for regions across 

Hawai‘i. The general approach involves:

• Collating into a relational database the enormous amount of 

count data (nearly 1 million records) gathered from almost 

500 variable circular plot surveys.

Hawaii Forest Bird Interagency Database Project: 

Collecting, Understanding, and Sharing Population Data on Hawaiian Forest Birds

 

• Integrating bird abundance with habitat information derived 

from digital maps of vegetation, elevation, and climate.

• Developing models of bird-habitat associations to predict 

abundance across the landscape and areas not surveyed.

• Determining the likelihood of detecting individuals of a species given the effects of weather, observer ability, and time of 

day and year.

• Applying detection probabilities to observed bird abundance 

to account for unobserved individuals and adjust estimates of 

density and population size.

• Examining regional and state-wide trends in bird abundance 

and occurrence.

• Assessing the effectiveness 

of surveys in monitoring 

species status.

• Sharing data and study 

results with the public, 

researchers and resource 

managers.

The endangered ‘akiapo ̄ l ̄a‘au (Hemignathus munroi) uses its elaborate, 

two-part beak to extract insect larvae from the bark of tree trunks and 

branches. Sadly, its abundance has declined precipitously throughout 

much of its fragmented range. However, conservation practices that 

include forest restoration and the cultivation of Acacia koa (a valuable 

native hardwood tree) in proximity to native forest can provide foraging 

habitat and support high densities of ‘akiapo ̄ l ̄a‘au. (Photo © Jack Jeffrey) 

The ‘akepa (Loxops coccineus), an 

endangered honeycreeper. (Photo 

© Jack Jeffrey)
A collaborative partnership

The HFBIDP is the result of a unique collaboration between 

the USGS Pacific Island Ecosystems Research Center and a 

number of partner universities, private landowners, state and 

federal agencies, and non-governmental organizations. Partners 

collaborate by contributing survey data, financial support, and/

or helping disseminate results. Collaborators include: 

• Hawai‘i Division of Forestry and Wildlife

• Hawai‘i Cooperative Studies Unit – University of 

Hawai‘i at Hilo

• Kamehameha Schools

• National Science Foundation

• Natural Heritage Program – Hawai‘i

• The Nature Conservancy – Hawai‘i

• Pacific Cooperative Studies Unit – University of 

Hawai‘i at Mˉanoa

• US Fish and Wildlife Service

• US Forest Service

• US National Park Service

• USGS Hawai‘i Gap Analysis Program

• USGS Pacific Basin Information Node

• USGS Pacific Island Ecosystems 

Research Center

Application to Conservation Strategies

Protecting core bird populations. The identification 

of population concentrations can be used to prioritize 

habitats for conservation and monitoring. High priority 

areas can also serve as the basis for public and private 

landowners to develop conservation partnerships. For 

instance, research by the HFBIDP supports the monitoring 

and habitat protection activities of the ‘Ola‘a-Kˉılauea Partner ˉ -

ship for areas with high bird species richness on Hawai‘i Island. 

Significant populations shown to reside outside of areas managed for conservation may also result in changes to management planning and improved habitat protection.

Guiding habitat management. HFBIDP research also seeks to 

identify habitat available for restoration or bird reintroduction. 

Feral ungulate (pig, cattle, goat and sheep) removal in the newly 

acquired Kahuku Ranch parcel of Hawai‘i Volcanoes National 

Park is expected to improve degraded forest bird habitat, 

particularly for species such as Hawai‘i ‘elepaio (Chasiempis 

sandwichensis) and ‘ˉoma‘o that are dependent on food resources 

from the forest understory. Continued monitoring will be needed to assess how populations respond to management actions.

Observed bird abundance (colored points in graphic at top right) is modeled with habitat information to derive predicted abundance and distribution across the landscape (blue to red corresponds with low to high; 

bottom right). In this example, the distribution of ‘o ̄ ma‘o (Myadestes obscurus) abundance is shown for the Ka‘ ̄u District, Hawai‘i Island (inset, 

above). Forest is shown in green in these Landsat ETM images. 

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Assessing population trends. Detecting incipient downward trends in bird 

populations is a critical step in formulating conservation efforts. For example, 

analysis by the HFBIDP of declines 

in endangered and once-common bird 

populations on Hualˉalai Mountain, 

Hawai‘i Island, have lent added urgency 

to the state’s effort to complete ungulate 

removal in the Pu‘u Wa‘awa‘a Wildlife 

Sanctuary. Likewise, identifying upward 

trends can help validate past or current 

management actions. Native bird species 

have shown stable or increasing trends 

since the establishment of the Hakalau 

Forest National Wildlife Refuge on 

Hawai‘i Island. On-going studies by the 

The Hawai‘i Forest Bird Interagency Database Project has analyzed bird 

distributions and trends from almost 500 variable circular plot surveys 

throughout the state of Hawai‘i (left). (Photo by P.M. Gorresen) 

Hawai‘i ‘elepaio (top) and o ̄ ma‘o (above) are examples of native species 

that benefit from ungulate exclusion and the protection and restoration of 

the forest understory. (Photos © Jack Jeffrey)

The density of the endangered Hawai‘i Creeper (Oreomystis mana) has increased at the Hakalau 

Forest National Wildlife Refuge (right) since habitat restoration activities began there in 1985. The 

careful monitoring of bird trends can help managers evaluate the effectiveness of conservation 

practices. (Photo © Jack Jeffrey)

HFBIDP will help determine how feral 

ungulate removal and reforestation in the 

refuge affect bird recovery. 

Improving population monitoring.

Careful examination of survey data has 

made evident inefficiencies and limitations in current monitoring programs. 

The trends of rare species or those with 

highly variable abundance have been 

found to be poorly tracked with count 

surveys. Monitoring these species will 

require more focused efforts that examine 

other measures of status such as territory mapping, survival, reproduction, 

etc. Assessments of variability in bird 

numbers as a function of survey effort 

have also shown that there is a species-

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For more information:

See the HFBIDP website at the USGS Pacific Island 

Ecosystems Research Center: biology.usgs.gov/

pierc/HFBIDPSite/HFBIDPHome.htm

or contact: 

Thane K. Pratt, Research Wildlife Biologist

phone: 808/985-6129; email: Thane_Pratt@usgs.gov

Fact sheet written by:

Thane K. Pratt, USGS Pacific Island Ecosystems 

Research Center (PIERC);

Bethany L. Woodworth, USGS-PIERC;

Richard J. Camp, Hawai‘i Cooperative Studies Unit 

at the University of Hawai‘i at Hilo (HCSU) ; and

P. Marcos Gorresen, HCSU

specific “optimal” range of samples, below which trends might 

not be detected and above which cost exceeds gain in information. Analyses of survey data also indicate that multi-species 

surveys may not coincide with peak vocalization periods for 

certain species and thereby underestimate bird numbers. For 

such species, better survey timing can result in larger population 

estimates. For example, recent surveys targeting the endangered 

‘akiapˉolˉa‘au have shown the population in Ka‘ˉu, Hawai‘i Island, to be considerably larger than previously estimated.

Collaborative efforts and sharing analytical results. HFBIDP 

team members have worked with the Hawai‘i GAP Analysis Program to develop bird range maps and species richness 

models used for identifying geographic gaps and priorities in 

conservation areas. HFBIDP studies are also contributing to the 

development of long-term survey programs such as the 

Inventory and Monitoring Program of the National Park 

Service. In addition, statewide appraisals of species status and 

trends have been recently completed and have contributed to 

extinction risk designations by the World Conservation Union 

and to Hawai‘i’s Comprehensive Wildlife Conservation Strategy. Detailed regional studies of bird distribution and trends are 

being completed for all major forest bird populations. These 

analyses contribute to the management planning at private, state 

and federal levels.

Identifying the interface of bird populations and disease 

zones. The mapping of predicted bird numbers can quantify the 

proportion of a population and the extent of bird habitat that lie 

within or outside areas harboring avian disease. About one-third 

of the ‘i‘iwi (Vestiaria coccinea; above) range in Ka‘ˉu is located 

Photo © Jack Jeffrey

between 1,000 and 1,500 meters, a zone at which avian malaria 

(Plasmodium relictum) transmission is considered to be high 

and which may be contributing to declining numbers of ‘i‘iwi

in the region. Bird distribution maps can help identify the areas 

in which the establishment of ungulate exclosures would be 

most effective in reducing the habitat disturbance that promotes 

disease transmission.