Data Zone
Justification of Red List category
This species is restricted to the twin islands of Biak-Supiori so may have a relatively small population, but there are insufficient data to quantify its population size. The population is suspected to be declining due to an ongoing slow rate of forest cover loss. The small range indicates that the species may be at risk, although the population is not severely fragmented. Forest loss is ongoing, hence a continuing decline in the area, extent or quality of habitat is estimated. Accordingly, Biak Triller is assessed as Near Threatened.
Population justification
The population size has not been quantified, but the species is described as widespread and common (Bishop and van Balen 2023).
Trend justification
The only identified threat to this species is habitat loss and degradation. There has been a slow rate of forest cover loss in the species' range, up to 4% in the three generations to 2022 (data from Global Forest Watch 2023, using Hansen et al. [2013] data and methods disclosed therein) and this is suspected to be causing broadly equivalent reductions in population size of this species.
Lalage leucoptera is restricted to the twin islands of Biak and Supiori, in the Cenderawasih Bay in north West Papua, Indonesia.
It inhabits selectively logged and primary forest, and less commonly degraded forest and lightly wooded farmland (Bishop and van Balen 2023). Its diet is assumed to be similar to Lalage atrovirens: fruit and arthropods foraged from the mid-storey and canopy (Taylor et al. 2020).
Forest on Biak has come under heavy pressure from logging and subsistence farming, with large patches converted to smallholder farms, indigenous gardens and/or coconut plantations (Bishop and van Balen 2023), though large-scale logging has not been economically feasible for some time (Wikramanayake et al. 2002). The rate of forest cover loss recorded through satellite monitoring has been slow in the past two decades, and in the three generations to 2022, the maximum rate is estimated at 4.0% (Global Forest Watch 2023, using Hansen et al. [2013] data and methods disclosed therein). Much of Supiori comprises virtually impenetrable, forested limestone mountains, which are likely to be safe from habitat degradation.
Conservation Actions Underway
The species is assumed to be present in the 110 km2 Biak-Utara protected area and throughout the 420 km2 Pulau Supiori Nature Reserve (UNEP-WCMC 2021a,b), both of which comprise virtually impenetrable limestone areas (Wikramanayake et al. 2002).
Conservation Actions Proposed
Conduct surveys on both islands to establish its current distribution and population status and assess its habitat requirements. Afford formal protection to further key sites where appropriate.
19 cm. A black and white triller similar to Black-browed but with far more extensive white in the wing, forming a continuous band from the greater coverts to the tertials.
Text account compilers
Haskell, L.
Contributors
Butchart, S., Dutson, G., Ekstrom, J. & Martin, R.
Recommended citation
BirdLife International (2025) Species factsheet: Biak Triller Lalage leucoptera. Downloaded from
https://datazone.birdlife.org/species/factsheet/biak-triller-lalage-leucoptera on 05/01/2025.
Recommended citation for factsheets for more than one species: BirdLife International (2025) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 05/01/2025.