||Puaiohi, Small Kauai Thrush
||17 cm. Small, dark thrush. Adult dark brown above, medium grey below, with pale eye-ring, dark moustachial streak and pale throat. Pink legs and feet. Juvenile heavily spotted above, buff below, scalloped with dark brown. Similar spp. Kama'o M. myadestinus larger, plumper, with shorter, heavier bill and dark legs. Introduced Melodious Laughingthrush Garrulax canorus brighter cinnamon-brown with yellow bill. Voice Song a short, sneezy burst of high, liquid trill notes. Call a short rasping hiss. Hints Secretive, but can be found occasionally on Alaka`i Swamp Trail near Koke`e.
|Red List Category & Criteria:
||Camp, R., Donaldson, P., Fretz, J., Gorresen, M., Leonard, D., Lepson, J., Roberts, P., Scott, J., Snetsinger, T., VanderWerf, E., Wakelee, K. & Woodworth, B.
||Benstead, P., Bird, J., Derhé, M., Harding, M., Isherwood, I., Stattersfield, A., Stuart, T., Symes, A. & Wright, L
This species qualifies as Critically Endangered because it has an extremely small range, wholly confined to one upland area where habitat quality is continuing to decline. It has apparently always been rare, although the reasons for this are unclear and the range and population trends are difficult to judge, because it is extremely elusive, and occurs in some areas that are difficult to access. Reintroduction of captive-bred individuals has however led to a significant population increase and if declines in habitat quality are halted the species may be eligible for downlisting in the future.
|Previously published Red List assessments:|
- 2013 – Critically Endangered (CR)
- 2012 – Critically Endangered (CR)
- 2009 – Critically Endangered (CR)
- 2008 – Critically Endangered (CR)
- 2004 – Critically Endangered (CR)
- 2000 – Critically Endangered (CR)
- 1996 – Critically Endangered (CR)
- 1994 – Critically Endangered (CR)
- 1988 – Threatened (T)
|Range Description:||Myadestes palmeri is endemic to Kaua`i in the Hawaiian Islands (USA), where recent records are all from the Alaka`i Wilderness Preserve. It was lost from the Waiau and possibly the Halekua drainages (T. Snetsinger per P. Donaldson in litt. 1999), but may be expanding its range in the Mohihi drainage (Snetsinger et al. 1999). It formerly occurred in lowland habitats, but probably only locally, and was extirpated from these areas by the end of the 19th century (J. Lepson in litt. 1999, Snetsinger et al. 1999, Burney et al. 2001). During 1998-2000, the population was estimated at c. 200, possibly up to 300, wild individuals (Lieberman and Kuehler 1998, Conrow 1999, Snetsinger et al. 1999, T. Snetsinger in litt. 2000), and more recently estimated at 500 individuals (range 200-1,000) in 2010 (KFBRP unpubl. data, in Puaiohi Working Group and Hawaiian Forest Bird Recovery Team 2010). Few birds were detected after two hurricanes in the 1990s, but the population size is thought to have recovered to pre-hurricane numbers (Pratt 1994, Conant et al. 1998, Snetsinger et al. 1999). A captive breeding programme began in 1996 and has facilitated the successful reintroduction of individuals into the wild annually since 1999, with 200 birds released as of 2010 (Puaiohi Working Group and Hawaiian Forest Bird Recovery Team 2010), resulting in successful breeding in the wild by captive-bred birds, although no known new subpopulations have yet been permanently established.|
United States (Hawaiian Is.)
|♦ Continuing decline in area of occupancy (AOO):||Unknown|
|♦ Extreme fluctuations in area of occupancy (AOO):||No||♦ Estimated extent of occurrence (EOO) - km2:||32|
|♦ Continuing decline in extent of occurrence (EOO):||Unknown||♦ Extreme fluctuations in extent of occurrence (EOO):||No|
|♦ Number of Locations:||1||♦ Continuing decline in number of locations:||Unknown|
|♦ Extreme fluctuations in the number of locations:||No||♦ Lower elevation limit (metres):||1050|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The population was estimated at 500 individuals (range 200-1,000) in 2010, roughly equivalent to 130-670 mature individuals (KFBRP unpubl. data, in Puaiohi Working Group and Hawaiian Forest Bird Recovery Team 2010). Previous estimates, derived from Conrow (1999), Lieberman and Kuehler (1998), Snetsinger et al. (1999), T. Snetsinger in litt. (2000), and P. Roberts in litt. (2007) totalled 200-500 individuals, roughly equivalent to 130-330 mature individuals.|
Trend Justification: Thanks to a captive breeding and reintroduction programme in the Alaka'i Wilderness Preserve, the species has more than doubled its population over three generations (13.5 years).
|Current Population Trend:||Increasing|
|♦ Number of mature individuals:||130-670||♦ Continuing decline of mature individuals:||No|
|♦ Extreme fluctuations:||No||♦ Population severely fragmented:||No|
|♦ No. of subpopulations:||1||♦ Continuing decline in subpopulations:||Unknown|
|♦ Extreme fluctuations in subpopulations:||No||♦ All individuals in one subpopulation:||Yes|
|♦ No. of individuals in largest subpopulation:||100|
The destruction of the understorey by feral pigs has been implicated in this species's rarity (Kepler and Kepler 1983). Avian pox-like lesions have been observed on a mist-netted bird (Herrmann and Snetsinger 1997), and avian malaria is suspected to cause some mortality (Snetsinger et al. 1999, K. Wakelee in litt. 1999). Currently, there are no forested areas on Kaua‘i where the mean ambient temperature prevents the seasonal incursion of malaria; mosquitoes and malaria can survive across all parts of the island, at least periodically. An increase in temperature of 2° C would result in an 85 % decrease in the land area on Kaua‘i where malaria transmission currently is only periodic (Benning et al. 2002). Between 2007-2009, 56 wild Puaiohi were tested for malaria and 11 (19.6%) were determined to be infected, an increase on 1 bird in 7 between 1994-1997 (Atkinson and Utzurrum 2010, in Puaiohi Working Group and Hawaiian Forest Bird Recovery Team 2010). At least three captive birds that died soon after release were determined to be infected with malaria. Thus, disease may limit Puaiohi from inhabiting low elevation areas with suitable nesting habitat.
Although hurricanes have caused serious damage to its habitat, the species appears to recover relatively well, probably because ravines are better sheltered (Conant et al. 1998, Snetsinger et al. 1999). Predation by native Short-eared Owls (Asio flammeus) and alien mammals (e.g. rats) suppresses productivity and competition for food with introduced insects, birds and mammals may also have negative impacts (Snetsinger et al. 1999, Snetsinger et al. 2005). Several plants, including blackberry (Rubus argutus), Australian Tree Fern (Cyathea cooperi), Kahili Ginger (Hedychium gardnerianum) Daisy Fleabane (Erigeron annuus) and Strawberry Guava (Psidium cattleianum) have significantly altered areas currently and recently occupied by Puaiohi, and have the potential to convert the forest canopy, understorey and cliffs used for nesting substrate to unsuitable habitat (P. Roberts in litt. 2007).
Conservation and Research Actions Underway
It is protected in the Alaka`i Wilderness Preserve. Rat poison bait stations have placed near a few nests with moderate success (Snetsinger et al. 1999). Bait stations are also placed around the release sites for captive-bred individuals at the time of release. Several types of rodent-resistant nest boxes have been installed in nesting habitat, and one pair was documented to nest successfully in one box. Control of feral ungulates has proved difficult in less accessible areas of the Alaka`i Wilderness Preserve, which is rarely visited by hunters, and alternatives are expensive and of limited effectiveness (USFWS 2003). An ungulate exclusion fence is planned for a portion of the Alaka'i plateau, which will include 5-10% of the species's range. A captive population was established in 1996, and 14 birds were released into the wild in 1999 (Lieberman and Kuehler 1998, Conrow 1999, USGS News Release 1999, T. Snetsinger in litt. 2000), with releases continuing subsequently and 200 birds released as of 2010 (Puaiohi Working Group and Hawaiian Forest Bird Recovery Team 2010). The captive-bred birds have bred with each other and with wild birds (USGS News Release 1999). Results of the releases have been mixed, with birds released in 1999-2001 surviving better than birds released from 2002-2006. The release strategy for 1999-2001 was highly successful, with 31 out of 34 released birds surviving at least one month after release and confirmed breeding occurring in the wild (USFWS 2003). From 2002 through 2007, roughly half of released birds survived for one month or longer. However from 2005-2011, long-term survival of 123 captive-bred birds was very low and it was concluded that the release of captive-bred birds has had little effect on the wild population in recent years (VanderWerf et al. 2014). Research on the factors limiting the species and the potential of management actions is ongoing.
Conservation and Research Actions Proposed
Develop a species-specific survey method and resurvey the entire population, searching for captive released birds and for areas of suitable unoccupied habitat. Determine disease prevalence and factors promoting transmission of avian pox and malaria, and explore disease management options (Puaiohi Working Group and Hawaiian Forest Bird Recovery Team 2010). Research suggests that reducing nest predation by controlling rats may be the best available management option (VanderWerf et al. 2014). Continue to conduct research to determine the impacts of predation and habitat degradation by alien species. Begin the process of phasing out the captive release programme. Continue and expand outreach. Investigate feasibility of translocations to higher islands (Puaiohi Working Group and Hawaiian Forest Bird Recovery Team 2010).