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

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
passerine first arrived to Kaua„i and was subsequently blown to Hawai„i Island and then O„ahu after
different storms. The entire species is absent from other islands in the State. It is likely that these
subspecies may eventually be separated into three species due to genetic evidence and plumage
differences (VanderWerf 2007).
The „elepaio is a nonmigratory, highly curious bird. Pairs are monogamous and territorial throughout
the year. The young remain with their parents for 9 months, during which time they are taught
foraging behaviors. After leaving the nest, the young remain within 0.6 mi of their parents.
The „elepaio was given its name due to the sound of its song. Males sing to defend their territory and
attract mates. This song is generally answered by the female‟s two-note call. Although „elepaio are
territorial during the entire year, this behavior is more prevalent immediately before and during nest
construction. As a result, they do not generally call during the nonbreeding season. Compared to
subspecies on the other islands, the Hawai„i „elepaio has the most phases and frequencies in their
calls (VanderWerf 2007).
Currently, Hawai„i „elepaio can be found in forested areas above 2,000 ft. Known populations occur
in Kohala and on the western slope of Mauna Kea. The estimated islandwide population is about
150,000 individuals (Mitchell et al. 2005).
Approximately 138,900 ( 605 SE) Hawai„i „elepaio occur in the North Hāmākua study area. Of this
total, roughly 27 percent of the population (or 38,000 birds) occur in the HFU. The primary
concentration within the study area occurs in the southerly portion of the upper elevation forest, just
south of the Refuge. Surveys conducted during a 24-year study period (1977- 2000) between the
months of February-July resulted in 5,537 „elepaio observations. During a 14-year study period
(1987-2000), the mean density of „elepaio specifically within the HFU was 2.57 birds per 2.47 acre.
No trends in density were observed during either of these study periods (Camp et al. 2003).
Higher densities of „elepaio occur in upper-elevation, closed-canopy, high-stature forests compared
to the lower degraded, open forests. More specifically, „elepaio densities were positively influenced
by „ōhi„a, high-stature forests, and elevation. In contrast, variables negatively associated with density
include grass, open or sparse canopy, midstature forest, presence of matted ferns, banana poka,
Psidium, slope, temperature, and rainfall (Camp et al. 2003).
Except for the O„ahu „elepaio, this species appears to be less affected by human disturbance than
most native Hawaiian birds due to their high adaptability. „Elepaio are able to utilize a variety of
habitats, employ various behaviors to search for and capture prey, and consume a wide range of
invertebrates. Foraging techniques range from gleaning to hanging and aerial hawking. „Elepaio are
also able to survive in both native and nonnative forests from dense rainforests to dry, open
woodlands in a wide range of elevations (VanderWerf 1998, 2007). Though avian disease is a
concern for Hawai„i „elepaio as well, they have also shown to have a greater immunity to avian
diseases compared to other native Hawaiian forest birds. Hawai„i „elepaio showed recovery 4-years
after an outbreak of the pox virus at the HFU in 1992 (VanderWerf 1998). However, recent evidence
indicates that the species‟ low -elevation range may be decreasing on Hawai„i Island (Camp et al.
2003).
Chapter 4. Refuge Biology and Habitats 4-37