Justification of Red List category
This rather inconspicuous warbler is listed as Vulnerable on account of its very small range and population. If further research shows that its population is declining or fluctuates with natural events, it may be uplisted to a higher category of threat.
The population is estimated to number 700-1300 individuals, roughly equating to 470-870 mature individuals.
There is no evidence of any long-term population changes, thus the species is suspected to be stable.
Phylloscopus amoenus is endemic to the extinct volcano of Kolombangara, Solomon Islands, where it has been recorded above c.1,200 m and is presumed to occur to the summit at 1,740 m, at least on the Northeastern side (C. Filardi in litt. 2012). Its total range is therefore 21 km2, although much of this is unsuitable, being open forest on the inner slopes of the volcanic caldera. No more than two pairs have been recorded on any one visit, but it is estimated that the population could number 1,000-2,000 individuals. At the highest elevations on Kolombangara this bird appears to be the second most abundant passerine, behind Hermit White-eye Zosterops murphyi, with loose groups of 6-8 individuals encountered at times (C. Filardi in litt. 2012). There is no evidence of any long-term population changes (Buckingham et al. 1995, G. Dutson pers. obs. 1998, M. Iles verbally 1998, Hornbuckle 1999a).
It inhabits mossy forest and has not been recorded from the large areas of open forest and scrub growing on landslide-damaged areas of the very steep crater. Singles and pairs forage low in the stunted forest, sometimes on moss-covered tree-trunks and on the ground; often in mixed species foraging flocks. Its nest is unknown (Buckingham et al. 1995, G. Dutson pers. obs. 1998, M. Iles verbally 1998).
Although the montane forest is under no threat from forestry, it is often damaged by landslides so that the (small) population can be expected to fluctuate with habitat availability. It may be threatened by introduced mammalian predators such as feral pigs and rats which have been recorded from montane forest on Kolombangara (M. Iles verbally 1998). The species does not seem to descend to elevations lower than 1,400 m and so habitat may be very limited (C. Filardi in litt. 2012). Climate change may further narrow the species's range.
Conservation Actions Underway
The montane forest has been declared a forest reserve by the company which has logging rights to most of the island (M. Iles verbally 1998). The entire island above 400 m elevation is now under strict protection for biodiversity values by a partnership between the forestry company, KFPL, and a legally registered customary landholder organization, the Kolombangara Island Biodiversity Conservation Association (KIBCA). The area is slated to be recognized in the new national Protected Areas Act when regulations are fully gazetted for the act.
11 cm. Small, stout, dumpy warbler. Heavy bill and long, stout legs are dark horn. Long, fine supercilium contrasts with dark forehead, fading into dreary olive upperparts with faint wing-bar. Underparts paler and brighter with obscure streaks. Similar spp. Island Leaf-warbler P. poliocephalus slighter with longer tail, brighter supercilium, greyer head with slight coronal stripe and plain yellow underparts. Voice Jumble of three to six high-pitched notes, shorter and sharper than P. poliocephalus and metallic tzik call. Hints Listen in the highest, mossy forest, where it forages in pairs, usually on moss and epiphyte-laden branches.
Text account compilers
Derhé, M., Dutson, G., Ekstrom, J., Mahood, S., Pilgrim, J., Stattersfield, A.
Iles, M., Dutson, G., Filardi, C.
BirdLife International (2023) Species factsheet: Phylloscopus amoenus. Downloaded from http://datazone.birdlife.org/species/factsheet/kolombangara-leaf-warbler-phylloscopus-amoenus on 25/09/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://datazone.birdlife.org on 25/09/2023.