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

Justification of Red List category
This leaf-warbler is endemic to Kolombangara, where it is confined to a very small area of small forest and is inferred to have a small population size. However, there is no known impacting threat and the population is likely stable. It therefore qualifies as Near Threatened.

Population justification
Confined to a very small area on Kolombangara, from 1,200 m to (presumably) the summit of Mt Veve at 1,740 m (C. Filardi in litt. 2012). Its range therefore comprises only 21 km². It is said to be uncommon (Dutson 2011) or rare (Buckingham et al. 1992) but data (eBird 2022) suggest it is encountered no less regularly than other leaf-warblers in the region and two visits in 2017 and 2019 found the species with relative ease in a small area once suitable elevations were reached (J. Bergmark pers. comm. 2022). Phylloscopus warblers typically occur at a relatively high density, with other montane species recorded at densities of 55-210 birds/km² (Evans et al. 1991, 1993; Marsden 1998). Adopting the 25th and 75th percentile of this range, and assuming an occupancy of c. 70%, the population is inferred to number c. 1,400-2,500 birds, or c. 900-1,650 mature individuals. These numbers are broadly congruent with Buckingham et al. (1992) who suggested the population size numbered 900-2,100, although it is unclear how this figure was arrived at, or whether it refers to individuals or mature individuals.

Trend justification
Suspected to be stable. Reports have consistently suggested no threat is acting on this species (Buckingham et al. 1992, G. Dutson in litt. 2012, J. Bergmark in litt. 2022) removing it from logging risk. Although the data are too sparse to analyse, the species appears to have become no scarcer comparing eBird (2022) data across time series over the last ten years.

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).

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' range, although there is no indication yet this is impacting this species.

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 recognised in the new national Protected Areas Act when regulations are fully gazetted for the act.

Conservation Actions Proposed
Establish a more accurate population estimate. Compare population densities in forests on inner and outer slopes of caldera. Map and measure the area of different forest-types. Monitor numbers in the most accessible areas. Investigate potential impacts of climate change on the species' range. Develop reforestation and habitat recovery actions for high elevation habitat. Investigate the occurrence of and threats posed by introduced predators. If found to be appropriate, begin control measures against introduced mammals.

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
Berryman, A., Vine, J.

Contributors
Dutson, G., Iles, M. & Filardi, C.

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Recommended citation
BirdLife International (2024) Species factsheet: Kolombangara Leaf-warbler Phylloscopus amoenus. Downloaded from https://datazone.birdlife.org/species/factsheet/kolombangara-leaf-warbler-phylloscopus-amoenus 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.