• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Justification of Red List category
This species 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 areas that are highly inaccessible. It has an extremely small range, wholly confined to one upland area where it is highly vulnerable to stochastic events and habitat quality is continuing to decline. It is therefore assessed as Critically Endangered.

Population justification
The species has apparently always been rare, though the reasons for this are unclear and the range and population trends are difficult to judge because it is extremely elusive and occurs in highly inaccessible sheltered ravines. Based on data collected in 2011-2013, the population was estimated at 494 breeding individuals (95% CI 414-580) by linking occupancy surveys to habitat characteristics, territory density, and landscape attributes (Crampton et al. 2017), and there is no more recent estimate (L. Crampton in litt. 2023).

Trend justification
The population, whilst small, appears to be stable (Crampton et al. 2017). Since the 1960s the species' range has contracted, with the species no longer found at lower elevations (Scott et al. 1986). 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). The most recent population estimate is 494 breeding individuals (95% CI 414-580) using data from 2011-2013, and previous estimates of 300-500 (using data from 1995–1998) and 270-525 birds (using data from 2003–2005) were extrapolated from surveys on a smaller proportion of streams within the range (Snetsinger et al. 1999, Woodworth et al. 2009, Crampton et al. 2017, USFWS 2018). Based on these data the population is assumed to have been stable since the mid-1990s (Crampton et al. 2017, USFWS 2018), though trends are difficult to determine given the lack of consistent methodologies (Fantle-Lepczyk et al. 2018). There is no more recent population estimate (L. Crampton in litt. 2023), with standard forest surveys being an unreliable sampling method for this species given its occurrence in highly inaccessible steep, narrow stream valleys (Crampton et al. 2017, Paxton et al. 2020). 
Population models have indicated a declining population under baseline conditions, though this contradicts assumptions that the population remains stable and may be due to inaccuracies in parameter estimation (Fantle-Lepczyk et al. 2018). Further study to refine mortality and reproductive estimates and to establish whether the population is stable or declining is urgently required, however even presumed to be stable the population remains highly restricted and susceptible to ongoing threats and stochastic events (Fantle-Lepczyk et al. 2018). Reintroduction of captive-bred individuals failed to lead to a significant population increase (Switzer et al. 2013); until declines in habitat quality are halted and predation by introduced mammals is addressed, the species will likely not recover. 

Myadestes palmeri is endemic to Kaua`i in the Hawaiian Islands (USA), where it is confined to stream valleys and associated ridges above 1,050 m elevation on the southern and central plateau of Alaka‘i Swamp. It was lost from the Waiau and possibly the Halekua drainages (T. Snetsinger per P. Donaldson in litt. 1999), but after Hurricane Iniki it appeared to slightly expand its 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). 

It is now restricted to high-elevation `ohi`a forests of the Alaka‘i Wilderness Preserve at 1,050 to 1,300 meters. It is a ravine specialist, favouring stream banks with a rich understorey (Kepler and Kepler 1983, Scott et al. 1986, Conant et al. 1998). Many recorded nests have been placed in cliffs above streams. It is primarily frugivorous, with arthropods (particularly insects) forming an important dietary component (Kepler and Kepler 1983, Scott et al. 1986, Snetsinger et al. 1999). At least one bird died after malaria infection in the wild, but the species may be more tolerant of avian malaria than others (Herrmann and Snetsinger 1997, Snetsinger et al. 1999). Prevalence of malaria is increasing in this species, and survival of chronically infected birds was similar to that of uninfected birds (Atkinson et al. 2014, VanderWerf et al. 2014). Breeding is typically between March and August. It has potentially high but variable productivity, with pairs producing 0.4 to 4.9 young per year in three years of observation (Snetsinger et al. 1999); annual variation in number of offspring produced is correlated with breeding season precipitation (Fantle-Lepcyk et al. 2016). It is now the sole native frugivore on Kauai, and plays a major role in seed dispersal of native plants within its range (Kaushik et al. 2018).

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). Disease prevalence in more common species has increased at several locations within the range of this species (VanderWerf 2012). 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). Although long-term survival of chronically infected individuals has been shown to be similar to that of uninfected individuals and the species may be more tolerant of the disease than others (VanderWerf et al. 2014), it likely does have an impact on overall species survival and its absence from malaria-infected lower elevations suggests the disease has still limited the Puaiohi from inhabiting low elevation areas with suitable nesting habitat (Fantle-Lepczyk et al. 2020).
Other factors, such as degradation of native forest by non-native plants may also be limiting their range (Crampton et al. 2017). Several plants, including blackberry (Rubus argutus), Australian Tree Fern (Sphaeropteris 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 (Crampton et al. 2017, Fantle-Lepczyk et al. 2018). The destruction of the understory by feral pigs and goats has been implicated in this species' rarity (Kepler and Kepler 1983) and is an ongoing threat.
Predation by native Short-eared Owls (Asio flammeus) and alien mammals (e.g. Black Rats Rattus rattus and cats Felis catus) suppresses productivity and competition for food with introduced insects, birds and mammals may also have negative impacts (Snetsinger et al. 1999, 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). Nevertheless, the population remains highly susceptible to stochastic events; hurricanes have likely caused extirpations in some parts of the range (VanderWerf 2012) and represent a significant plausible future threat. Additionally, given evidence that previous wet season rainfall is associated with nest success of the species, forecasted changes in weather conditions due to anthropogenic climate change may negatively impact the population (Fantle-Lepcyk et al. 2016).

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). Research suggests that reducing nest predation by controlling rats may be the best available management option (VanderWerf et al. 2014, Fantle-Lepczyk et al. 2018). Ungulate and predator control is ongoing. Rat poison bait stations were placed near a few nests with moderate success (Snetsinger et al. 1999), and self-resetting Goodnature A24 traps to control rodents have been deployed in the Halehaha area, which is being additionally protected by an ungulate proof fence (Crampton 2016, Else 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. Research into effective nest box designs is ongoing (Fantle-Lepczyk et al. 2018). 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, with roughly only half of the birds released from 2002-2007 surviving for one month or longer. 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), possibly due to saturation of suitable habitat (USFWS 2018). 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 method to survey the entire population was developed in 2011 and was used to predict areas of suitable habitat from 2011-2013 (Crampton et al. 2017). 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. Funding to use song meters and field teams to survey these areas were conducted in 2017 (L. Crampton pers. comm.). 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). Development of genetic tools to reduce transmission of avian malaria is ongoing, and an experimental larval mosquito control program was initiated in Kawaikōī Stream of the NAR in 2016 (USFWS 2018).

Conservation and Research Actions Proposed
Monitor the population to determine response to management actions and effects of climate change (USFWS 2018). Continue to survey areas of suitable habitat that have not yet been surveyed. Continue and refine occupancy survey methods to provide a more accurate population estimate (Vanderwerf 2012). Finer scale habitat classification, better vegetation data and better topographic mapping is needed to further refine the population estimate (Crampton et al. 2017). Refine mortality and reproductive estimates to help improve model performance and refine population analyses (Fantle-Lepczyk et al. 2018). Further examine how hurricanes and variable rainfall may affect the species (Fantle-Lepczyk et al. 2018). Understand the levels of genetic diversity still extant in the population (Fantle-Lepczyk et al. 2018). Further understand disease resistance and the impacts of malaria on the species (Fantle-Lepczyk et al. 2018). Continue research in the fields of genomic technologies and genetically modified mosquitoes for disease control and their field application (USFWS 2018). 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. Investigate potential impacts of cats, owls and avian competitors (Fantle-Lepczyk et al. 2018). Continue habitat management in areas where the species currently exists (USFWS 2018). Expand rat control and provision of predator-proof nest boxes (Fantle-Lepczyk et al. 2018). Remove invasive plants and pigs to promote the return of native vegetation (Fantle-Lepczyk et al. 2018). Prevent additional introductions of invasive species (USFWS 2018). Continue and expand outreach. Investigate feasibility of translocations to higher islands (Puaiohi Working Group and Hawaiian Forest Bird Recovery Team 2010, Fantle-Lepczyk et al. 2020).

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.

Text account compilers
Vine, J.

Contributors
Camp, R., Crampton, L., Donaldson, P., Fretz, J., Gorresen, M., Leonard, D., Lepson, J., Masuda, B., Roberts, P., Scott, J.M., Snetsinger, T., VanderWerf, E., Wakelee, K. & Woodworth, B.

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Recommended citation
BirdLife International (2024) Species factsheet: Puaiohi Myadestes palmeri. Downloaded from https://datazone.birdlife.org/species/factsheet/puaiohi-myadestes-palmeri on 24/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 24/12/2024.