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

4.5.1 ‘I‘iwi (Vestiaria coccinea)
Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Male and female „i„iwi are primarily vermillion red, with a black tail and wings, and a long, decurved
pink bill. The juvenile is green with black spots and a shorter dusky bill, which becomes yellow then
pink with age.
The following island population estimates are based on Hawaiian Forest Bird Surveys (1976-1981):
340,000 ± 12,000 (95 percent CI) individuals on the Island of Hawai„i (88 percent in Hāmākua),
19,000 ± 2,000 (95 percent CI) individuals on east Maui, 180 ± 150 (95 percent CI) on west Maui,
80 ± 65 (95 percent CI) individuals on Moloka„i, and 5,400 ± 500 (95 percent CI) in the Alaka„i
Swamp on Kaua„i. Recent surveys (1996) suggest that O„ahu supports less than 50 birds. In 1988,
two birds were detected on Moloka„i. On Kaua„i, populations declined after the 1992 hurricane, but
changed little from 1994-2000. The overall population may be declining, but the species‟ wideranging
foraging complicates population estimates and the determination of long-term trends
(Mitchell et al. 2005).
From 1987-2000, a population of 285,422 + 1,267 (SE) „i„iwi was estimated to occur in the North
Hāmākua study area. Of this total, 100,347 birds (35 percent) were predicted to occur within the
HFU. „I„iwi mean density for the 14-year study period of surveys (1987-2000) within the HFU was
8.5 birds per acre (SD = 9.27). „I„iwi populations did not show a positive or negative trend in density
over the 14-year study period. However, a moderate increase in density did occur over the 24-year
study period (1977-2000) (Camp et al. 2003).
In the central windward region of Hawai„i, i„iwi were extirpated from the mid-elevation study areas
and are possibly in decline in Kūlani-Keauhou. Declines of „i„iwi have been observed elsewhere
within mid-elevation habitat suggesting that their ranges are contracting westward and upslope in the
central windward region (Gorresen et al. 2005).
„I„iwi density decreased at the high elevation site Kūlani-Keauhou between 1995-2003 (4.0-3.4 birds
per acre). However, inter-annual densities were fairly variable and differences may reflect local
movement in response to nectar availability instead (Ralph and Fancy 1995). At the Mauna Loa
Strip, „i„iwi were present at 0.04 birds per acre and did not exhibit increasing or decreasing trends. At
lower elevations, „i„iwi densities declined more than tenfold from 1977-1994 from 1.2-0.09 birds per
acre in the „Ōla„a study area and were not present at the East Rift (Gorresen et al. 2005).
At the HFU, densities of „i„iwi were highest in upper elevation (greater than 4,900 ft) in mesic and
wet koa/„ōhi„a and „ōhi„a forests of high stature and closed canopy. „I„iwi abundances were
positively associated with koa, presence of banana poka and elevation, and negatively associated
with grass, nonnative vegetation, and presence of tree fern. The positive association with P.
mollissima may be due to the use of its copious nectar by „i„iwi (Fancy and Ralph 1998). „I„iwi
occurred at low densities in heterogeneous habitats along the grass-forest interface and in midelevation
forest.
At the KFU, „i„iwi are found above 4,900 ft (Atkinson et al. 2005). Density estimates and habitat
preferences in this area have not been studied.
The „i„iwi is a common forest bird in mesic and wet koa-„ōhi„a and „ōhi„a forest above 4,900 ft. The
habitat on the windward slopes of Hawai„i receive 27.6-39.4 in of rainfall annually. „I„iwi are highly
4-32 Chapter 4. Refuge Biology and Habitats