DESCRIPTION AND TAXONOMY
The Kaua`i `ô`ô or `ô`ô `â`â is one of four known Hawaiian species of
Moho and one of five known Hawaiian bird species within the family
Meliphagidae. It is 19.5 centimeters (7.7 inches) long, shorter-tailed, and
somewhat smaller than the `ô`ô’s of the other islands, hence the, “`â`â,”
meaning dwarf `ô`ô. It is glossy black on the head, wings, and tail; smoky
brown on the lower back, rump and abdomen; and rufous-brown on the upper
tail coverts. It has a prominent white patch at the bend of the wing. The
throat feathers are black with a subterminal bar of white, giving a barred or
scaled effect. The thigh feathers are golden yellow in adults, but black in
immatures. The iris is dull yellow. The bill and feet are black, except for the
soles of the feet that are pale yellow (Berger 1972).
The song consists of loud whistles that have been described as flutelike,
hollow, echoing, and haunting. A call note was described as a distinct
“took-took” (Munro 1944). Nesting birds have been reported to use a “beep
beep” call (Scott et al. 1986).
LIFE HISTORY
Much of what is known about the life history of the Kaua`i `ô`ô was
learned by John L. Sincock who spent many months between 1967 and 1978
searching for and studying Kaua`i’s rare birds (Sincock et al. 1984). Its last
known habitat was dense native `ôhi`a (Metrosideros polymorpha) forest in
the deep stream valleys of the central Alaka`i Wilderness Preserve. The only
known nests were located in cavities of large dead `ôhi`a snags. One nest was
described as being 40 feet (12 meters) above the ground in a dead `ôhi`a tree
(Berger 1972). There is little information on the extent of the nesting season,
but two nestlings were reported in a single nest in June 1971, and two other
nests were monitored in late May and early June (Sincock 1982).
The diet is reported to be insects, spiders, millipedes, moths, crickets,
snails, `ôlapa (Cheirodendron) fruits, and nectar from `ôhi`a, lobelia, and
other flowering plants (Richardson and Bowles 1964; Sincock 1982). Early
ornithologists reported that `ô`ô fed heavily on the flower bracts of `ie`ie
(Freycinetia arborea), which was abundant in formerly occupied low
elevation forest habitat, but is not found in the upper elevation forests that
were last occupied.
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CURRENT AND HISTORIC RANGE AND POPULATION STATUS
The Kaua`i `ô`ô was reportedly very common from near sea level to
the high interior forests of Kaua`i up to the end of the 19th century, but after
only 3 decades it was thought to be close to extinction (Figure 19; Munro
1944). Except for inconclusive reports of possible vocalizations, it went
without observation until rediscovered by Donagho (1941) and again by
Richardson and Bowles (1961). Sincock located and described the first nest
in a tree cavity in 1971, and followed subsequent nests in 1972 and 1973.
Upon rediscovery during the late 1960’s, the Kaua`i `ô`ô population was
estimated at only 36 birds (Sincock et al. 1984). Only a single pair was found
during an intensive survey made in 1981 (Scott et al. 1986). Two hurricanes
that struck Kaua`i in 1982 and 1992, caused much forest damage that possibly
eliminated the remnant population. The last plausible record of a Kaua`i `ô`ô
was a vocal response to a recorded vocalization played by a field biologist on
April 28, 1987, in the locality of Halehaha/Halepâ`âkai Stream (Hawai’i
Department of Land and Natural Resources/J. Krakowski 1987 pers. comm.).
It is very likely that the Kaua`i `ô`ô is now extinct, because no subsequent
sightings or vocalizations have been documented despite three comprehensive
forest bird surveys in 1989, 1994, and 2000, and a rare bird search conducted
in 1996 (Reynolds and Snetsinger 2001).
REASONS FOR DECLINE AND CURRENT THREATS
As with several other endangered Kaua`i forest birds, the Kaua`i `ô`ô
was once considered a very common species in the lowlands as well as in
upland forests. The rather sudden decline in numbers noted during the first 2
decades of the 20th century (Munro 1944) points to a limiting factor that had
an acute impact on the species. Unfortunately, the Kaua`i `ô`ô is now so rare,
or probably extinct, that identification of threats and reasons for its decline is
difficult, if not impossible. Habitat destruction by agricultural development
obviously reduced their lowland range, but does not explain the sudden
decline noted in the interior uplands as well. After the turn of the century, a
large number of alien birds were introduced as many of the native lowland
birds disappeared. Some of these alien species may have harbored foreign
diseases or parasites for which the `ô`ô had little or no immunity. The
mosquito vector of blood-borne diseases was already well established, and
could have brought about a rapid decimation of a highly susceptible endemic
bird. The fact that Moho on other islands suffered a similar fate during
approximately the same period suggests disease as a major limiting factor,
coupled with the fact that the last `ô`ô were found only at higher mosquitofree
elevations. It is possible that the remote high elevation forests of Kaua`i
where the `ô`ô persisted was marginal habitat that may have lacked suitable
cavities for nest sites.
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The use of large old-growth snags for nesting and the paucity of any
large-timbered forests after the turn of the century may have limited the `ô`ô’s
ability to find suitable nest sites, particularly after two hurricanes struck
Kaua`i in 1982 and 1992. Cavity nests may also be more susceptible to
foraging rats known to be numerous in Hawai`i’s forests. Polynesian rats
(Rattus exulans) are presumed to have become established in the islands with
the arrival of the first Polynesian settlers (Tomich 1969). The black rat
(Rattus rattus) evidently established itself in Hawai`i after the advent of the
European explorers in the late 1700's. The demise of many of Hawai`i’s
forest birds seemed to have coincided with the arrivals of various new alien
fauna, yet the Kaua`i `ô`ô decline was apparently quite sudden, suggesting a
particular susceptibility to a single potent limiting factor. Other impacts on
their habitat, such as forest damage by feral pigs, goats, and the spread of
invasive plants, likely had a supplemental negative impact on the species.
CONSERVATION EFFORTS
The Kaua`i `ô`ô was federallylisted as endangered on March 11, 1967
(U.S. Fish and Wildlife Service 1967), became protected under the State of
Hawai`i endangered species law on March 22, 1982, and was included in the
Kaua`i Forest Birds Recovery Plan (U.S. Fish and Wildlife Service 1983b).
The Forest Reserve Act of 1903 was an important action that protected
watersheds in Hawai`i. Strengthened and re-titled, “Hawai’i Department of
Land and Natural Resources Title 13, Chapter 104, Rules Regulating
Activities Within Forest Reserves,” it protects native forest values from
certain degrading factors caused by human activities. The Hawai’i
Department of Land and Natural Resources established the 4,022 hectares
(9,938 acres) Alaka`i Wilderness Preserve in 1964 (Administrative Rule No.
1, Chapter 3), recognizing the value of the pristine forest of that area and the
need to control potential degrading factors.
A multi-agency research project aimed at the recovery of the critically
endangered puaiohi was initiated in 1995 (see puaiohi account). Information
about other endangered Kaua`i forest birds has been gained incidentally, but
unfortunately no Kaua`i `ô`ô have been observed during this project. Other
research by U.S. Geological Survey personnel is examining the threat from
alien diseases and alien vectors of disease, such as mosquitoes, on native
forest birds on Kaua`i (C. Atkinson/U.S. Geological Survey unpubl. data).
The Hawai`i Rare Bird Search Team made an intensive systematic effort to
locate any surviving endangered forest birds on Kaua`i, but no `ô`ô were
recorded during the search (Reynolds and Snetsinger 2001).
RECOVERY STRATEGY
See Rare Bird Discovery Protocol in Section III. D.
ecos.fws.gov/docs/recovery_plans/2003/031016.pdf
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