DESCRIPTION AND TAXONOMY
Early descriptions of the kâma`o were made by Stejneger in 1887 from
specimens provided to the Smithsonian Institution by Valdemar Knudsen in
the 1880’s (Munro 1944). Originally described as Phaeornis obscura
myadestina, Pratt (1982) offered convincing evidence that Phaeornis should
be merged with the American solitaire genus Myadestes, and that some
Hawaiian taxa formerly treated as subspecies are sufficiently distinct to merit
full species status.
The kâma`o is a medium-sized (20 centimeters, 7.9 inches) solitaire,
gray-brown above, tinged with olive especially on the back, and light gray
below with a whitish belly and under tail coverts. The legs are dark graybrown
and relatively short, but the ventral surface of the toes are pale yellow.
The eyes are dark and the bill is black. The kâma`o lacks the white eye-ring
and pinkish legs of the smaller puaiohi (small Kaua`i thrush). Immature birds
have a spotted appearance. The song is sweet and melodic, sometimes lavish
and flute-like, and is often given just before dawn and after dusk. A scolding
or hissing "police whistle" alarm note also has been described.
LIFE HISTORY
Little is known of the life history of the kâma`o, but presumably it is
similar in many respects to the more common and closely related `ôma`o or
Hawai`i thrush (Myadestes obscurus). The heaviest periods of singing occur
in the winter (January to March). Nesting likely occurs in the spring (April to
July). The nest has not been described, but may be a cavity or low platform as
with the `ôma`o. The eggs are grayish-white eggs with irregular reddishbrown
splotches, and the clutch size is one or two. The diet of the kâma`o is
reported to consist of fruits and berries, particularly the bracts of the `ie`ie
vine (Freycinetia arborea), as well as insects and snails (Munro 1944). The
kâma`o was often described for its habit of rising on the wing into the air,
singing a few vigorous notes and then suddenly dropping down into the
underbrush. Early in the morning it sings an elaborate song from treetops.
The kâma`o seems to spend less time on the ground than does the smaller
puaiohi.
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HABITAT DESCRIPTION
In the past half century the kâma`o has not been seen below 1,100
meters (3,500 feet) elevation. Early ornithologists noted the difficulties these
birds had with "lumps on their feet and sometimes at the corners of the
mouth,” which likely were avian pox lesions, transmitted by mosquitoes or
other vectors. In more recent years, kâma`o have been seen most frequently
where a healthy open forest canopy existed, primarily of `ôhi`a (Metrosideros
polymorpha) and `ôlapa (Cheirodendron spp.). A diverse understory, lush
with epiphytes, tree ferns, mosses, and a variety of native fruit-producing
plants, such as`ie`ie, `ôhâ wai (Clermontia spp.), and `ôhelo (Vaccinium spp.),
probably are associated with good kâma`o habitat. The `ie`ie vines highly
favored by the kâma`o still exist in some areas of the island, but not in the
higher elevations to which the birds may be currently restricted. That plant
does not thrive above 1,500 meters (5,000 feet) elevation (Wagner et al.,
1999). The fact that the kâma`o once existed near sea level, but now is
restricted to high elevation native forest without its most preferred food plant,
suggests that it may be surviving in marginal habitat.
HISTORICAL AND CURRENT RANGE AND STATUS
In 1881, the kâma`o was considered extremely common in the moist
forests near sea level on northern Kaua`i as well as in the upland interior
mountain forests. It was still considered common on the outer forest edges in
1899, but by 1928 it became difficult to find in the lower forests. In 1941, it
was still considered common in the upland interior forested plateau of the
Alaka`i Wilderness Preserve (Munro 1944). The kâma`o became noticeably
rare by the mid 1960’s. At this time it remained only in the uppermost
regions of the Alaka`i in very sparse numbers. From 1968 to 1973, Sincock et
al. (1984) found the kâma`o near the southern edge of the Alaka`i Wilderness
Preserve, although one isolated occurrence was reported in the upper
elevations of Kôke`e State Park (Figure 19, p. 137). In the summer of 1985,
two kâma`o were seen during an intensive 2-week survey of the Alaka`i. This
followed the moderately severe Hurricane Iwa that occurred in November
1982 (Hawai’i Department of Land and Natural Resources 1985). The last
confirmed observation of the kâma`o was made during the February 1989
Kaua`i forest bird survey (Hawai’i Department of Land and Natural
Resources 1989). The more recent hurricane named “Iniki” severely damaged
Kaua`i’s forests in September 1992. No sightings of kâma`o were made
during a brief post-hurricane survey made in February 1993 (Hawai’i
Department of Land and Natural Resources 1994), nor in more intensive
surveys conducted in February and March 1994 and March 2000 (Hawai’i
Department of Land and Natural Resources 1995).
Although the kâma`o has not been seen since 1989, it should be noted
that its smaller congener, the puaiohi or small Kaua`i thrush, went many years
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without being seen, but then began to reappear in small numbers. In view of
the kâma`o’s original widespread distribution to near sea level and the
apparent negative impact of avian diseases and the destruction of its lowland
habitat, it is unlikely that it will ever be restored to its historical range, but
recovery of a population in the upper Alaka`i plateau is remotely possible.
The fact that the kâma`o has not been seen since 1989 places this species on
the brink of extinction, if it is not already extinct.
REASONS FOR DECLINE AND CURRENT THREATS
Avian disease is by far the most significant factor suspected to limit
the kâma`o. Early historical observations were made of pox lesions on the
kâma`o at the lower edges of its mid-19th century range, indicating the
kâma`o was susceptible to alien diseases for which it had little or no
immunity. The fact that some good quality native forest with abundant fruitbearing
plants exists below their current range demonstrates that habitat
destruction cannot account for the extirpation of the species in the lowlands
and that factors other than habitat quality are limiting the population. The
proliferation of introduced fruits, such as blackberry (Rubus argutus), banana
passionflower (Passiflora mollissima), guava (Psidium cattleianum), and
thimbleberry (Rubus rosaefolius) into the mid-elevations, may have been an
attractive food source that enticed kâma`o into lower elevations where they
were exposed to avian diseases such as pox and avian malaria.
If kâma`o are cavity or low platform nesters, as solitaires generally
are, predators such as rats (Rattus spp.) may severely limit nesting success and
explain why some of the smaller arboreally nesting species have had a greater
degree of nesting success. Feral cats occasionally are found in high elevation
rain forest habitat, and young solitaires foraging on the ground are probably
one of the easier prey species for these predators.
Several introduced birds, including the Japanese White-eye,
Melodious Laughing-thrush (Garrulax canorus), and White-rumped Shama
(Copsychus malabaricus) share the same habitat with the kâma`o to some
degree and may compete with the kâma`o for food and nest sites. These and
other alien bird species, including the recently established Japanese Bushwarbler
(Cettia diphone), also may serve as reservoirs of disease.
Establishment of other potentially detrimental birds on Kaua`i, such as the
red-vented bulbul (Pycnonotus cafer) found on some of the other Hawaiian
Islands, remains a persistent threat.
Habitat degradation resulting from the invasion of pernicious alien
weeds has drastically changed the forest structure and integrity. Two
hurricanes in 1982 and 1992 severely disrupted portions of high quality native
forest, and have made space for the germination and expansion of noxious
weeds such as yellow ginger (Hedychium flavescens), daisy fleabane
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(Erigeron karvinskianus), glorybush (Tibouchina urvilleana), Japanese
honeysuckle (Lonicera japonica), and others (see Table 10, p. 191).
Feral pigs, and goats to a lesser degree, have had a long-term
damaging effect upon native forests in the remaining kâma`o range by
consuming and damaging understory vegetation, creating openings on the
forest floor for weeds, and transporting weed seeds into the forest. Soil
erosion and disruption of seedling regeneration of native plants is one of many
forest management problems in kâma`o range.
Perhaps less obvious, but potentially detrimental to the health of the
remaining kâma`o habitat, are introductions of new alien invertebrates to the
forest ecosystem. Although kâma`o are primarily frugivorous, insects and
spiders are likely to be an important component of the diet, especially for
nestlings. Introductions of predatory and parasitic invertebrates that compete
with native species for food pose a continuing threat throughout the islands.
Introduced predatory insects also may reduce or eliminate specialized native
insects that are necessary for pollination of certain food plants. Many of the
food plants used by kâma`o could be negatively affected by herbivorous alien
insects, such as the two-spotted leafhopper (Sophonia rufofascia), which may
reduce their range, fruit set, and eventual survival. Introduced snails that prey
on indigenous snails also could reduce food resources of the kâma`o. On the
other hand, the detrimental effects of some of these new insects and molluscs
could be somewhat offset if they are direct prey items of the kâma`o.
Finally, the remaining kâma`o population, if indeed it exists, is likely
to be extremely small and genetically impoverished, increasing the risks of
demographic instability and inbreeding depression.
CONSERVATION EFFORTS
So little is known about the kâma`o and other endangered Kaua`i
forest birds and their limiting factors that few species-specific conservation
actions have been attempted. Efforts have centered on protecting the integrity
of the remaining native forest habitat in the Alaka`i Wilderness Preserve
where these birds have survived in during the past half century. The Forest
Reserve Act of 1903 was an important action that protected watersheds in
Hawai`i, and it was strengthened and re-titled Hawai’i Department of Land
and Natural Resources Title 13, Chapter 104, Rules Regulating Activities
Within Forest Reserves, which 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.
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The kâma`o was federally listed as endangered on October 13, 1970
(U.S. Fish and Wildlife Service 1970), and it became protected under the State
of Hawai`i endangered species law on March 22, 1982.
Surveys and Monitoring. Regular surveys of Kaua`i forest bird
populations and habitat conditions in the Alaka`i Wilderness Preserve have
been conducted on established transects since the late 1960's. John L.
Sincock, Research Biologist with the U.S. Fish and Wildlife Service, Kaua`i
Field Station, conducted intensive status and distribution surveys of Kaua`i’s
forest birds from 1968 to 1973 (Sincock et al. 1984). Large scale, multiagency
surveys were conducted on established transects in 1981, 1985, 1989,
1993, 1994, and 2000 (Hawai’i Department of Land and Natural Resources
1981, 1985, 1989, 1993, 1994; Woodworth et al. in prep.).
Control of Feral Ungulates. The Hawai’i Department of Land and
Natural Resources has maintained liberal public hunting seasons to minimize
forest damage caused by feral pigs and goats within the Alaka`i Wilderness
Preserve for several decades. Unfortunately, public hunting succeeds only in
the more accessible areas of the preserve, and ungulate populations in more
remote areas remain quite high. Alternatives are of limited effectiveness,
expensive, and logistically difficult. Very limited aerial reconnaissance and
shooting of feral goats and pigs has been attempted in the most remote
regions, but has not been economically effective.
Information and Education. Materials featuring Kaua`i’s
endangered forest birds, as well as those found on other islands, have been
published and provided to schools to assist in the effort to inform the public
and gain support for conservation of endangered species. Privately funded
filmmakers including the British Broadcasting Company and National
Geographic Society have produced documentaries that inform the public of
the plight of endangered forest birds. Several articles have appeared in
popular nature magazines and local newspapers to increase public awareness
of issues related to the conservation of Hawaiian forest birds, including those
on Kaua`i.
RECOVERY STRATEGY
The kâma`o is so critically rare, if not already extinct, that no specific
recovery strategy can be devised at this point other than to include it within
the general framework of the Rare Bird Discovery Protocol outlined in
Section III. D.
Although the kâma`o has never been managed in captivity, it is
reasonable to assume that many of the same techniques that have proven
successful for the `ôma`o and the puaiohi (egg collection, artificial incubation
and rearing, captive propagation, and reintroduction) would prove effective
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with this congeneric solitaire species. If a breeding pair or nest is ever found,
the eggs, nestlings, or juveniles should be collected to establish a captive
population.
ecos.fws.gov/docs/recovery_plans/2003/031016.pdf
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