Monitoring Hawaiian Biodiversity: Changes to forest birds and their habitat

Science Center Objects

Hawaiian forests are beset by many stressors, resulting in a complex pattern of altered ecosystems, impeirled species, and (in some areas) substantial protection and restoration. Short-term studies focused on specific sites or biota have limited value in understanding landscape-level change. Long-term and spatialy extensive data are needed to understand how ecosystems are reacting to both stressor and active management. 

Overview:

Hawaiian forests are beset by many stressors, resulting in a complex pattern of altered ecosystems, imperiled species, and (in some areas) substantial protection and restoration. Short-term studies focused on specific sites or biota have limited value in understanding landscape-level change. Long-term and spatially extensive data are needed to understand how ecosystems are reacting to both stressor and active management. 

Vegetation data collection

Vegetation and bird surveys from the 1970s and 1980s were repeated in 2015 to document any changes. Photo: J. Jacobi

The conservation crisis facing Hawaiian ecosystems has been met by a concerted effort to survey and monitor the abundance, distribution and trends of many species throughout the islands. Perhaps the most notable of these efforts were the state-wide surveys of forest bird and plant communities in the 1970s and 1980s as part of the Hawaiian Forest Bird Survey (HFBS). The results of this historic effort provided the basis for many plant and bird recovery plans and land acquisition and management decisions in Hawai‘i.

The HFBS systematically characterized plant and bird communities across transects spanning all major islands (except O‘ahu). This extensive dataset has now been organized into databases and geographic information systems, and this baseline provides an opportunity to assess how forest ecosystems and its constituent bird and plant populations have changed over time. As part of the HaBiTATS (Hawaiian Biodiversity Trends Across Time and Space) project, a select area on Hawai‘i Island was surveyed in 2015 with the objective of demonstrating the potential of using the HFBS methodology to reassess the status of bird and plant communities across multiple geographic regions and islands. The results of the comparative study presented herein highlight examples of the apparent vulnerability and resiliency of native-dominated Hawaiian ecosystems. 

Project Objectives:

The objective of this work is to understand changes in biodiversity across large areas of the hawaiian forest landscape, and to provide information on the drivers of ecosystem change over the last 30 years.

Specific study objectives are to:

  1. collect information on plant and bird species community composition, abundance and spatial distribution;
  2. assess changes in several biodiversity metrics; 
  3. examine changes in the distribution of invasive non-native species as well as changes in land use as potential drivers of native biodiversity patterns, and
  4. demonstrate field and data analysis methods that may be applied to a large-scale biodiversity monitoring program..
Apapane perched on a branch

‘Apapane perched on a branch. Photo: R. Kohley

Highlights and Key Findings:

Our comparative analysis of the 1977 and 2015 surveys demonstrated considerable change in the both the plant and bird communities within the study area. Select endemics considered to be keystone plant species (e.g., Acacia koa and Metrosideros polymorpha) showed little change in occurrence, in part perhaps because this group is mostly comprised of long-lived tree species. However, considerable change was noted in the occurrence and distribution of other plant species. 

Except for the ‘apapane, the abundance and distribution of native forest bird species was lower in 2015 compared to 1977. Non-native bird species abundance and occurrence patterns were mixed: 7 species observed in 1977 were not detected in 2015, whereas 6 species were newly detected in the latter survey. Some widespread species showed no change (Japanese white-eye), others declined (Red-billed leiothrix), and some newly established species (Japanese bush-warbler) are now abundant in the study area. The abundance and species richness patterns for both natives and non-natives were particularly prevalent at elevations below 1,500 m.

The patterns observed for native birds in this study largely conform to that expected from disease-related factors. However, future climate change is projected to cause significant decreases in the abundance and diversity of the remaining Hawaiian bird communities.

2015 Progress:

All field work for this project has been completed this year and analyses have been conducted. A manuscript summarizing the results is currently being prepared and will be completed in early 2016.

2016 Planned Work:

In 2016 we will be preparing a manuscript for publication that summarizes the results of this study.