Pacific Island Bird Survey Design and Data Analysis

Science Center Objects

Abundance data are collected for bird populations throughout the Pacific Islands by numerous federal, state, university, and non-profit organizations. In order to ensure data are standardized and available to researchers throughout the region, interagency bird databases have been created and continue to be used. These databases contain more than a million compiled, proofed, and standardized records collected over the past 40 years.

Overview:

Abundance data are collected for bird populations throughout the Pacific Islands by numerous federal, state, university, and non-profit organizations. In order to ensure data are standardized and available to researchers throughout the region, interagency bird databases have been created and continue to be used. These databases contain more than a million compiled, proofed, and standardize records collected over the past 40 years.

These survey data represent a valuable informational resource that has not previously been accessible.  Analysis of historical data is now largely complete, but analysis and reports of new survey data, grounded in the historical data, continue to provide important information for managers.  These reports provide updated distribution maps and population estimates (for both native and non-native bird species), examine population trends, and develop habitat suitability models.  The database and results are also being made available to scientists and natural resource managers throughout Hawai‘i.  Analysis of the data will ultimately: elucidate trends in distribution and density of species of concern (both endangered and invasive species), help test hypotheses for the causes of decline, be used to examine the results of management actions, and guide future survey effort, conservation planning and decision-making.

Project Locations:

Kilauea caldera with steam

Halema‘uma‘u crater, Kilauea Volcano, Hawai‘i Island. Photo: USGS

Pacific Island National Parks - Inventory & Monitoring: The National Park Service has implemented a strategy designed to institutionalize natural resource inventory and monitoring on a programmatic basis throughout the agency. The effort was undertaken to ensure that the approximately 270 park units with significant natural resources possess the resource information needed for effective, science-based managerial decision-making and resource protection.  The three main components of the strategy are completion of basic resources inventories, creation of experimental prototype monitoring programs to evaluate monitoring designs and strategies, and implementation of operational monitoring of critical parameters in all natural resource parks. The minimal inventory information required by parks includes a natural resource bibliography, base map data, a geology map, soils map, weather data, air quality data and location of monitoring stations, water body classification, water quality data, vegetation map, documented lists of vertebrates and vascular plants, and data on species distribution and status of vertebrates and vascular plants. Prototype monitoring programs at more than 10 parks or clusters will design and test monitoring protocols and serves as examples of successful monitoring program development.  Monitoring programs in all natural resource parks will be developed to determine status and trends of selected indicators of the condition of park ecosystems, to provide early warning of abnormal conditions, to provide data to understand the dynamic condition of park ecosystems and serve as reference points for comparisons with more altered environments, to contribute to legal and Congressional mandates related to natural resource protection and visitor enjoyment, and to measure progress toward performance goals.

Hakalau forest landscape

Hakalau Forest National Wildlife Refuge. Photo: USGS

Hawaii U.S. Fish & Wildlife Refuges: Since October 1999, the Hawaii Forest Bird Interagency Database Project (HFBIDP) has been compiling, proofing, and standardizing records from over 500 forest bird surveys conducted throughout Hawaii by 22 different agencies and organizations spanning the past 30 years. These survey data represent a valuable informational resource that has not previously been accessible.  Analysis of historical data is now largely complete, but analysis and reports of new survey data, grounded in the historical data, continue to provide important information for managers. These reports provide updated distribution maps and population estimates (for both native and non-native bird species), examine population trends, and develop habitat suitability models.  The database and results are also being made available to scientists and natural resource managers throughout Hawaii. The data will ultimately be used to elucidate trends in distribution and density of species of concern (both endangered and invasive species), test hypotheses for the causes of decline, examine the results of management actions, and guide future survey effort, conservation planning and decision-making.

View of Nihoa from the west with seabirds flying in the foreground

View of Nihoa Island from the west, with seabirds flying over head. Photo: C. Farmer

Nihoa: The Nihoa millerbird (Acrocephalus familiaris kingi) and Nihoa finch (Telespiza ultima) are endangered passerine birds endemic to Nihoa Island, part of the Hawaiian Islands National Wildlife Refuge (HINWR) in the Papahānaomokuākea Marine National Monument. The refuge extends about 1300 km along the northwestern chain of Hawaiian Islands, with the exception of Midway and Kure Atolls, and consists of islands, reefs, and atolls that include Nihoa Island, Necker, French Frigate Shoals, Gardner Pinnacles, Maro Reef, Laysan Island, Lisianski Island, and Pearl and Hermes Reef. The many small islands provide bare rocky, lowland shrub and grass, sand, and wetland habitat for over 30 species and 14 million breeding sea birds, wintering shorebirds, and endangered endemic songbirds and waterfowl. Nihoa is unlike any of the other northwestern Hawaiian Islands with its 275-m cliff, basalt rock surface, and tiny beach. This small island is about 1 square km in size and is at the southeastern end of the northwestern island chain. In addition to the two endemic land birds, Nihoa is home to 72 terrestrial arthropods, including giant crickets and earwigs, an endangered fan palm and shrub, and other native plants.

Reducing extinction risks to the endemic Nihoa millerbird and Nihoa finch requires understanding their population trends to be able to project anticipated trajectories, evaluate the potential impact of translocation, and prioritize management actions. The current survey protocol has produced a wide range of annual population estimates for both species. For example, between 1967 and 2009 millerbird point estimates ranged from 30 to 814. In addition, within-year variability was considerably high; e.g., the 95% confidence limits for the 2009 millerbird population spanned 312 to 969 birds. The very high variability in these estimates makes determining the actual population size and assessing management actions problematic. It also severely hinders the timely appraisal of population trends. For example, with a goal of 90% statistical power, to detect a statistically significant decline it would take more than 50 years to detect a 50% decline and several centuries to detect a 25% decline in the millerbird population given the inter-annual variability exhibited by previous estimates (average coefficient of variation [CV] from 1967 to 2009 is 0.4). Consequently, long periods of surveys are required before statistically significant trends can be determined.

The present program of sampling and monitoring on Nihoa was originally developed to estimate population size and track trends, but the program has not been evaluated to determine whether it meets these general objectives in a manner that usefully informs management decisions. For example, can the present program detect a trend within a specified period for a given level of statistical risk? Moreover, the bird survey data collected periodically since 1967 has not been applied towards an adaptive revision of survey methods and sampling effort. That is, given the survey results to date, should the bird monitoring program on Nihoa be modified, and if so, what are the various candidate sampling designs that can meet both general and specific monitoring objectives?

We tested and evaluated survey methods to improve the accuracy of density and population estimates for the Nihoa millerbird and Nihoa finch. A final report and journal manuscript are available.

 

Palila eating mamane seeds

A color banded and radio tagged palila eats māmane seeds. Photo: USGS

Mauna Kea, Hawai‘i Island: The palila (Loxioides bailleui) is an endangered species of Hawaiian honeycreeper which exists only in subalpine forests dominated by māmane (Sophora chrysophylla) and naio (Myoporum sandwichense) on Mauna Kea Volcano. The diet of this finch-billed bird is unusually restricted; immature seeds, flowers, and insects found on māmane trees are critical to its existence. Māmane also is the preferred nesting substrate of the palila. Federal court orders have resulted in efforts to reduce populations of introduced feral sheep and mouflon sheep within Palila Critical Habitat, because they eliminate most mamane regeneration and modify forest structure. U.S. Fish and Wildlife Service specified mitigation of the effects of realigning Saddle Road (Highway 200) through Palila Critical Habitat to include restoration research to guide the conservation of palila within their core range and to develop techniques for reestablishing a population within a portion of former range. In addition, cattle grazing leases were withdrawn to allow forest restoration in areas formerly occupied by palila. The U.S. Army has also agreed to manage former palila habitat within Pohakuloa Training Area for palila restoration. The concentration of palila in dry, highly flammable subalpine forest increases the threat of extinction due to many factors. Of greatest concern is the reduction of habitat carrying capacity resulting from long-term browsing by introduced sheep and the likelihood that drought severity and frequency is increasing due to climate change. Managers need both comprehensive ecological information for developing management strategies and practical information and techniques to effectively restore populations and habitats.

Guam & Commonwealth of the Northern Mariana Islands: 

The birds of the Mariana Islands, an archipelago in the western Pacific, are threatened by rapid economic development and the spread of non-native species, particularly a devastating predator, the brown tree snake (Boiga irregularis). The Mariana Islands, an archipelago of 15 islands east of the Philippines, is one of the Endemic Bird Areas of the Pacific identified by BirdLife International and is a biodiversity hotspot within Micronesia. The older islands in the southern portion of the archipelago are volcanic in origin but are composed of uplifted, terraced limestone terrain derived from ancient coral reefs. The northern islands are stratovolcanoes. The native land bird avifauna of the Mariana Islands is composed of 19 species, of which 16 have highly restricted ranges and 10 are endemic to the archipelago. Most of the endemic birds are closely related to species on other nearby Pacific islands, except for the golden white-eye (Cleptornis marchei), which is a monotypic genus. Over the past several centuries, the Mariana avifauna has withstood environmental changes brought about by ever-increasing human settlement, war, and international commerce. Nevertheless, the introduction of the brown tree snake to Guam after World War II eliminated 13 of 22 native breeding birds.

Hope for the remaining Mariana avifauna now lies with the islands north of Guam - Rota, Aguiguan, Tinian, and Saipan - the main islands comprising the Commonwealth of the Northern Mariana Islands (CNMI). Although there have been recent reports of the brown tree snake from some islands of the CNMI, particularly from the most populous island, Saipan, surveys have not yet demonstrated the existence of a breeding population. Nevertheless, without intensive interdiction efforts, the snake will likely soon establish itself in the CNMI, if it has not already done so. Other invasive species also pose serious threats to the CNMI avifauna through predation and habitat alteration, and further research may identify how competition and disease are affecting native birds. These newly emerging alien species have arrived with the exchange of goods and trade as part of ongoing globalization. Civilian and military effects on birds and habitats in the CNMI also are major concerns, especially on the most populated islands of Saipan, Tinian, and Rota. Invasive species and economic development have been the cause for the extinction or decline of many bird species in Oceania, and these same factors pose similar threats to conservation in the CNMI as well. The USGS can provide significant technical assistance to the U.S. Fish and Wildlife Service (USFWS) and CNMI Division of Fish & Wildlife (DFW) by developing methods for conducting effective bird survey and monitoring programs and by analyzing and interpreting data to determine population abundance and trends.