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

Justification of Red List category
This lorikeet has a single, small population which is inferred to be declining from observations of a recent reduction in apparent abundance, thought to be as a result of capture for the bird trade compounded by forest loss and degradation. It therefore qualifies as Vulnerable.

Population justification
A preliminary population estimate based on expert knowledge is of 3,000-4,000 individuals, based on rates of encounter within the range of the species (M. Halaouate in litt. 2012). Hence the population size was estimated to fall in the wider band of 2,500-9,999 mature individuals. With reports of a recent notable reduction in abundance a re-estimation of the density and population size is required, but in the absence of a new estimate the existing value is retained.

Trend justification
Recent reports suggest that the species is undergoing a rapid and concerning population reduction. Visiting birdwatchers have noted that the species was very difficult to locate in 2019, while it was common five years previously (Bergmark 2019). Encounters remain regular however, with most visits to the island seeking endemic birds still locating the species (Bergmark 2019, Bocos 2019).

T. rosenbergii is endemic to the twin islands of Biak-Supiori, Indonesia. It has apparently become uncommon within the past decade (Bergmark 2019, Bocos 2019), with the last stronghold the remaining forests of Supiori (M. Halaouate in litt. 2013). The area of forest, as derived from the 'GlobCover 2' land classification GIS layer (Arino et al. 2012), is estimated at 1,572 km², after the exclusion of fragments smaller than 1 km². If all of this was occupied by the species would result in a maximum area of occupancy (AOO) of 2,780 km². Given the recent reports of the species becoming much more difficult to observe, the true area now occupied is suspected to be smaller than this, but is uncertain as the species is thought to travel widely across the island in search of flowering trees (Mayr and Meyer de Schauensee 1939).

Its habitat requirements are assumed to be similar to other Trichoglossus lorikeets in being found in primarily lowland forest including secondary growth and including plantations (del Hoyo et al. 1997). Mayr and Meyer de Schauensee (1939) report that it is found in deep forest more than Eos (cyanogenia). At this time, it occurred in groups of 5-6 travelling rapidly over forest ('jungle') between flowering trees. Otherwise, there is little specific information.

Trapping for the bird trade may be the cause of reported recent population reductions with direct observations of the export of parrots from Biak to Java (M. Halaouate in litt. 2012). Papua is noted as a major source for parrots (Indraswari et al. 2020), including the Trichoglossus haematodus group (Setiani and Ahmadi 2020) but there is no quantification of trade from Biak and this is an urgent area of required research.
Forest on Biak has come under heavy pressure from logging and subsistence farming, though large-scale logging has not been economically feasible for some time (Wikramanayake et al. 2002). Significant tracts of forest remain in the largely inaccessible areas of Biak Utara and Supiori, considered secure. The rate of forest cover loss recorded through satellite monitoring has been slow in the past two decades, and over the past three generations of the species the maximum rate is estimated at 3.6% (Global Forest Watch 2021, using Hansen et al. [2013] data and methods disclosed therein).

Conservation and research actions underway
CITES Appendix II. CMS Appendix II. The species is present in the 110 km² Biak-Utara protected area and throughout the 420 km² Pulau Supiori Nature Reserve (UNEP-WCMC 2021a,b).

Conservation and research actions proposed
Estimate population and assess population trend and scale of trapping pressure. Conduct a targeted survey for the species to identify important sites, with a view to affording them protection. Conduct research into its status and habitat use (with particular regard to feeding ecology and forest fragmentation).
Initiate awareness campaigns to elicit the support of local people in protecting forests and preventing illegal trade. Ensure the effective protection of tall forest in the Biak-Utara protected area.

25-30 cm. A brightly-coloured lorikeet with dark blue head, extensive yellow hindneck to top of mantle, broadly dark indigo barred red breast and flanks and indigo belly, with the rest of the upperparts and tail bright green. Bill red. Similar spp. T. rosenbergii differs from the other Trichoglossus species in the very heavy indigo barring on the breast, indigo belly and extensive yellow on the hindneck.

Text account compilers
Martin, R.

Contributors
Dutson, G., Halaouate, M., Harding, M., Symes, A. & Taylor, J.

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Recommended citation
BirdLife International (2024) Species factsheet: Biak Lorikeet Trichoglossus rosenbergii. Downloaded from https://datazone.birdlife.org/species/factsheet/biak-lorikeet-trichoglossus-rosenbergii on 23/11/2024.
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 23/11/2024.