Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
predictions of models, including habitat characteristics, oceanic condition indices, weather,
predator/parasite indices, global climate change forecasts, etc. Cluster spatial locations surveyed
across each of the reforested pastureland, open forest, and closed forest regions for reanalysis as
spatial replicates to estimate dynamics of Hakalau birds using the best models identified.
Estimate the magnitude of the effect of increasing abundance of Japanese white eyes on ‘ākepa over
the past 20 years by applying the best available models to annual population estimates for both
species in closed forest and open forest regions of the Refuge. Evaluate effects of habitat restoration
using best models above applied to spatial replicates identified above.
Organize, train, supervise, and provide logistical support for observers. Conduct and analyze paired
observer variable circular plot survey to obtain unbiased abundance estimates for endangered, native
and nonnative bird species occupying upper elevation newly reforested abandoned pasture lands and
mid-elevation open forest and closed forests of Hakalau NWR.
Cost Estimate: $140,000
C) Foraging ecology and competition among native and nonnative forest bird species at
Hakalau Forest NWR
A detailed knowledge of feeding ecology is important to the conservation of Hawaiian forest bird
populations and their habitats. Recent studies have indicated that populations of many feeding
specialists have declined historically, in part because food webs have been disrupted by nonnative
species. A wide range of nonnative species have been identified as potential competitors for
important foods of Hawaiian forest birds; nevertheless, much attention has focused on the role of
nonnative bird species, particularly the introduced Japanese white-eye, which is a widespread and
generalist forager.
Studies have inferred the existence of competition between native forest birds and Japanese whiteeyes
through analyses of population distributions, demographic changes, or reductions in juvenile
sizes and weights of native species. Claims that the foraging behavior of Japanese white-eyes and
native bird species overlap sufficiently to be causing food limitation, leading to a severe decline in
numbers of ‘ākepa at Hakalau Forest NWR need to be further evaluated. A quantitative evaluation of
the degree of overlap between forest bird species in foraging behavior or the use of resources will be
useful in this evaluation.
Preliminary analyses of fecal samples from Hakalau Forest NWR indicate relatively little overlap
between native and nonnative bird species in the use of arthropod prey (U.S. Geological Survey
unpublished data). Additional research is needed on the foraging behavior of bird species. In
particular, it is important to determine the degree of overlap in the use of habitat types, plant species,
and foraging substrates (e.g., foliage, small branches, large branches, etc.). Results from these studies
will help managers evaluate threats from nonnative species and assess their options for protecting
populations of endangered bird species.
Research will identify the means by which forest bird species at Hakalau Forest NWR obtain food
over time and space, determine how bird species partition resources, and directly assess the extent to
which species may compete for food due to overlapping niche requirements. This research will
evaluate overlap among species in the use of:
1. habitat types (e.g., old-growth forest, planted koa stands, other plantings);
C-16 Appendix C. Plan Implementation