Data Zone
Justification of Red List category
This species has a very small population likely belonging to several small subpopulations. Although there is uncertainty surrounding the species due to a lack of recent records, available data are indicative of a decline since 1984 and this is thought to be continuing given the likely ongoing threats. It is therefore assessed as Endangered.
Population justification
The population has not been robustly estimated since 1984 when numbers were estimated at 2,168 (Engbring et al. 1990). In the absence of more recent and complete data, and accounting for the fact that only a proportion likely refer to mature individuals, the population is tentatively placed in the range 1,000-2,499 mature individuals. There is evidence however that the species has likely declined since the 1984 estimate (see Population trend), and an up-to-date quantification of the population size is urgently required. There is an urgent need to collect up-to-date information on populations from the Faichuk group, particularly Tol South and Polle where relatively large numbers were recorded in 1984.
Trend justification
This species is thought to occur at highest densities in native forest which is subject to deforestation and contains non-native species (Engbring et al. 1990, SPREP 2001), and may continue to be under threat from population pressures which are causing ongoing habitat degradation throughout Chuuk (R. Davis in litt. 2023). Observations in 2001 suggested that it had declined to lower population densities compared to 1984 (G. Dutson in litt. 2003). On Tol South, no birds were found in a visit in 1991 and only 3-4 birds in 1993, although birds were seen again in 2005 (C. Collins in litt. 2005). It was thought to have been extirpated from Weno after a major fire destroyed the patch of forest where it was uncommon in the 1970s (H. D. Pratt in litt. 1994); however, two males were seen in Sopo Forest in 2005 (C. Collins in litt. 2005). The species now appears to be rare on Weno (C. Collins in litt. 2011), and according to local people it is becoming rarer on Tol South (D. Scott in litt. 2011). It was not found in 2010 in an area on Dublon Island where it had been seen in 2008 (D. Scott in litt. 2011). In 2022, sound recorders were used to capture the aural landscape at stations previously surveyed in 1984, however difficulties regarding access permissions meant that only 130 of 579 stations could be resurveyed (O'Brien 2023). The species was present at 17 of these 130 stations in 1984, but no calls were isolated from the recordings made in 2022 (O'Brien 2023). Although this may be partly due to restricted knowledge of the repertoire of this species, it is a considerable concern especially considering the overall lack of monitoring data and no access to the population currently being possible. Precautionarily therefore, the population is inferred to be declining overall.
Metabolus rugensis is widely but sparsely distributed on all, or nearly all, of the high lagoon islands, as well as some of the outer reef islets of Chuuk, Federated States of Micronesia.
It occurs at highest densities in small patches of upland native forest, but is also found in well-developed stands of mangrove, thickets, atoll strand and (rarely) plantations along scrubby slopes, often covered by hibiscus Hibiscus tiliaceus or along steep ridges or cliffs (Engbring et al. 1990, D. Scott in litt. 2011). It favours areas with a thick, leafy understorey where it is found in small family groups gleaning insects, lizards and other prey from the foliage (Engbring et al. 1990). It appears to be strongly territorial, nesting in trees with dense foliage and nesting has been recorded from April to July (Engbring et al. 1990).
It is likely to have declined dramatically in the 1940s, owing to extensive agricultural development during the Japanese administration. Although it shows some flexibility in its habitat requirements, the species appears to prefer native forest, which on Tol South is now restricted to the summit plateau (D. Scott in litt. 2011). Previous observations from Tol South suggest that only subsistence-level timber extraction is now occurring, owing to the topography of the island and areas of difficult terrain (C. Collins in litt. 2011, D. Scott in litt. 2011). However, the species is thought to occur at higher densities in native forest (Engbring et al. 1990) and conversion to agriculture has been considered a threat (SPREP 2001). The species may continue to be under threat from population pressure which is causing ongoing habitat degradation across Chuuk (Gregory 2020, R. Davis in litt. 2023). Additionally, acoustic recordings from Onei suggest that human intrusion may be high in some parts of the range (M. O'Brien in litt. 2023). The extent and spread of invasive species including plants, rats and cats within the range is also a concern, though the impacts of these are largely unknown (SPREP 2001; M. O'Brien in litt. 2023). There are also second-hand reports that the species has been targeted with slingshots on Weno (C. Collins in litt. 2011). The species is potentially threatened by extreme storm events given its extremely restricted range, a threat that could potentially be exacerbated by climate change.
Conservation Actions Underway
This species is the state bird of Chuuk and may obtain some conservation benefit from this recognition.
20 cm. Large, striking flycatcher. Adult male nearly all white, with glossy blue-black face and throat and black primary tips. Some are tinged pale salmon or buff below. Females dark slate, most individuals blotched with rufous feathers retained from juvenile plumage. Juveniles bright rufous above, rufous-buff below with ill-defined, buff eyebrow. Similar spp. Juveniles similar to Caroline Reed-warbler Acrocephalus syrinx, but much brighter rufous above and with less defined supercilium. Voice No well-defined song. Calls include human-like whistles slurred up or down and plaintive, querulous u-waw, reflected in the local name. Hints Slow-moving and rather tame, but surprisingly difficult to see.
Text account compilers
Vine, J.
Contributors
Collins, C., Dutson, G., Pratt, H.D., Scott, D., O'Brien, M. & Davis, R.
Recommended citation
BirdLife International (2024) Species factsheet: Chuuk Monarch Metabolus rugensis. Downloaded from
https://datazone.birdlife.org/species/factsheet/chuuk-monarch-metabolus-rugensis on 23/12/2024.
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 23/12/2024.