Justification of Red List Category
The species is remarkably poorly-known with a tiny number of modern records, frustrating attempts to estimate range size, population size and trend. Consequently the species is classified as Data Deficient. A reassessment of the effort to date in areas where the species would have been expected to be encountered may prompt a listing of this species at a high threat category.
The global population size has not been quantified, but the species is described as extremely rare (del Hoyo et al. 2005).
The population is suspected to be stable in the absence of evidence for any declines or substantial 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), 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, but were it to be a lowland species it would have been severely negatively affected by habitat loss over the past few decades.
Conservation Actions Underway
No targeted conservation actions are known for this species.
Text account compilers
Taylor, J., Symes, A., Westrip, J., Benstead, P., Martin, R
Duckworth, W., Williams, R.
BirdLife International (2019) Species factsheet: Pycnonotus nieuwenhuisii. Downloaded from http://www.birdlife.org on 15/09/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 15/09/2019.