Data Zone
Justification of Red List category
This species is among the most poorly known in Asia. First, there is considerable uncertainty over whether its status as a species is valid, with alternative suggestions in the literature that it is either (1) a morph of another species; or (2) a hybrid. These hypotheses remain to be tested. Second, the species is known from only two specimens (one from Sumatra in 1900, one from Borneo in 1937) and observations made in Brunei in 1992. While this suggests it to have a Sundaic distribution, the paucity of sightings since, in a relatively well-explored part of Asia, makes determining its range (and the likely threats within it) impossible. For these reasons, it is classified as Data Deficient.
Population justification
Impossible to determine. It is known from only two specimens, both taxonomic types, and observations in Brunei from more than 25 years ago (see Collar 2014). If the species is indeed valid, the paucity of records may ostensibly suggest it is very rare, although Pycnonotus bulbuls are rarely so, and the area of lowland forest within this species' range (which is relatively well explored), is vast.
Trend justification
Undetermined. The confusion over its range and taxonomic status, as well as the total absence of data on its breeding biology, precludes the identification of likely threats.
Pycnonotus nieuwenhuisii is known from north-east Kalimantan (one specimen collected at 600 m in 1900) and Sumatra (one specimen collected at 700 m in 1937), Indonesia, and Brunei, where single birds were seen on five occasions in 1992 in Batu Apoi National Park (Collar et al. 1994). It is unusual for a species of bulbul to be widespread but to occur at such low densities, so this form may represent an extremely rare morph of another species or else hybrids (see Collar 2014; Eaton et al. 2016, 2021), although it could be a genuinely rare habitat specialist that is occasionally forced to search other areas for food (Williams 2002).
The Sumatran specimen was collected in secondary scrub in pasture land, while the 1992 Brunei sightings occurred in lowland dipterocarp forest at c.60 m (Williams 2002).
It is unknown whether the species is currently affected by any threats.
Conservation Actions Underway
No targeted conservation actions are known for this species.
Text account compilers
Berryman, A.
Contributors
Benstead, P., Duckworth, W., Martin, R., Symes, A., Taylor, J., Westrip, J.R.S. & Williams, R.
Recommended citation
BirdLife International (2024) Species factsheet: Blue-wattled Bulbul Pycnonotus nieuwenhuisii. Downloaded from
https://datazone.birdlife.org/species/factsheet/blue-wattled-bulbul-pycnonotus-nieuwenhuisii 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.