||Myadestes palmeri (Rothschild, 1893)
||Puaiohi, Small Kauai Thrush
||del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
||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:
||Butchart, S. & Symes, A.
||Camp, R., Donaldson, P., Fretz, J., Gorresen, M., Leonard, D., Lepson, J., Roberts, P., Scott, J., Snetsinger, T., VanderWerf, E., Wakelee, K., Woodworth, B. & Crampton, L.
||Benstead, P., Bird, J., Derhé, M., Harding, M., Isherwood, I., Stattersfield, A., Stuart, T., Symes, A., Wright, L, North, A.
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 failed to lead to a significant population increase (Switzer et al. 2014); until declines in habitat quality are halted and predation by introduced mammals is addressed, the species will not recover. However, the population, whilst small, appears to be stable (Crampton et al. submitted).
|Previously published Red List assessments:|
- 2015 – Critically Endangered (CR)
- 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 after Hurricane Iniki appeared to slightly expand its population range in the Mohihi and other drainages (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). Currently, it is estimated at 487 individuals (Crampton et al. submitted). 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 that began in 1996 led to the release of 237 captive bred birds, although a few captive-bred birds successfully bred in the wild, survival and recruitment of captive bred birds was generally poor and the programme has been discontinued (Switzer et al. 2013; VanderWerf et al. 2014; The Garden Island 2016). |
United States (Hawaiian Is.)
|♦ Continuing decline in area of occupancy (AOO):||No|
|♦ Extreme fluctuations in area of occupancy (AOO):||No||♦ Estimated extent of occurrence (EOO) - km2:||43|
|♦ Continuing decline in extent of occurrence (EOO):||No||♦ Extreme fluctuations in extent of occurrence (EOO):||No|
|♦ Number of Locations:||1||♦ Continuing decline in number of locations:||No|
|♦ 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 487 breeding individuals (95% CI 405-579 birds) in 2013 (Crampton et al. submitted). 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. However, because these estimates did not encompass the entire range, the population is assumed to have been stable in size across the 1999-2013 time period (Crampton et al. submitted).|
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:||Stable|
|♦ Number of mature individuals:||405-579||♦ 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|
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; at least three captive birds that died soon after release were determined to be infected with malaria (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 2007-2013, 66 wild Puaiohi were tested for malaria and 11 (22.7%) were determined to be infected, whereas 0 of 7 were infected between 1994-1997 (Atkinson et al. 2014). Thus, disease may limit Puaiohi from inhabiting low elevation areas with suitable nesting habitat. However, long-term survival of chronically infected individuals is similar to that of uninfected individuals (VanderWerf et al. 2014), so other factors, such as degradation of the native forest by non-native plants may also be limiting their range (Crampton et al. submitted).
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). The destruction of the understory by feral pigs has been implicated in this species's rarity (Kepler and Kepler 1983).
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). Low female and juvenile survival likely limits its rate of increase; at least some female and nestling mortality is caused by predation of rats at nests (VanderWerf et al. 2014; L. Crampton pers. obs), and rats also likely take recently fledged birds. Although hurricanes have caused serious damage to its habitat, the species appeared to recover relatively well, probably because ravines are better sheltered (Conant et al. 1998, Snetsinger et al. 1999).
Conservation and Research Actions Underway
It is protected in the Alaka`i Wilderness Preserve and portions of the fenced Hono O Na Pali Natural Area Reserve (KHON2, 2014). Rat poison bait stations were placed near a few nests with moderate success (Snetsinger et al. 1999), and currently approximately 200 Goodnature A24 traps control rodents in the Halehaha area, which is currently being fenced with an ungulate proof fence to be completed in 2016 (Else 2016; Crampton 2016). Several types of rodent-resistant nest boxes have been installed in nesting habitat in Mohihi and Kawaikoi, and one pair was documented to nest successfully in one box. 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). Releases continued subsequently until 2012, with a total of 222 birds released (Switzer et al. 2013). The captive-bred birds bred with each other and with wild birds (Switzer et al. 2013). Birds released in 1999-2001 survived and reproduced 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). Furthermore, the captive flock was suffering from inbreeding depression (B. Masuda pers. comm). Thus the captive breeding programme has been discontinued and all healthy captive-bred Puaiohi were released into the wild in 2016 (The Garden Island, 2016). Research on the factors limiting the species and the potential of management actions is ongoing. A species-specific survey method to survey the entire population was developed in 2011, and used and to search for captive released birds and predict areas of suitable habitat from 2011-2013 (Crampton et al. submitted). This effort confirmed that likely high density areas of Puaiohi have already been identified, but indicated other areas likely to host low-moderate densities of Puaiohi that have not yet been surveyed.
Conservation and Research Actions Proposed
Continue to survey areas of suitable habitat that have not yet been surveyed. Funding to use song meters and field teams to survey these areas will be conducted in 2017 (L. Crampton pers comms). Studies of disease prevalence and factors promoting transmission of avian pox and malaria, and disease management options are ongoing (Puaiohi Working Group and Hawaiian Forest Bird Recovery Team 2010, Crampton 2016). Research suggests that reducing nest predation by controlling rats may be the best available management option (VanderWerf et al. 2014); an experimental rat trapping programme with self-resetting GoodNature A24 traps was initiated in 2015, expanded in 2016 and will continue through 2017 (Crampton 2016). This study combines assessment of the efficacy of the traps in reducing rodents and impacts on nest success. Continue to conduct research to determine the impacts of predation and habitat degradation by alien species. Ungulate-proof fencing (completed, ongoing and proposed) will facilitate this research. Continue and expand outreach. Investigate feasibility of translocations to higher islands (Puaiohi Working Group and Hawaiian Forest Bird Recovery Team 2010).