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

Justification of Red List category
Forest cover loss in this species' range is rapid. Even though it is somewhat tolerant of habitat degradation it is still suspected to be declining at a moderately rapid rate. This species is also affected by hunting for the pet trade. For these reasons it is assessed as Near Threatened.

Population justification
The global population of this species remains un-estimated. In oil palm plantations it appears to be too rare to generate reliable population densities (see Yahya et al. 2020) while in primary forest it has been recorded at densities of c.1.16 birds/km² in southern Thailand (Kempt et al. 2009). The species is often described as common or uncommon (del Hoyo et al. 1999, Wells 1999, Eaton et al. 2021) and appears relatively adaptable to habitat modification, occurring too in isolated park fragments in cities (eBird 2021).

Trend justification
Using a previous three-generation length period (27.9 years), and based on forest loss between 2000 and 2012, Tracewski et al. (2016) estimated this species to have lost 26% of its habitat. Although the three-generation period is now shorter (22 years; Bird et al. 2020), the rate of forest loss in the range of this species has accelerated since 2012, such that forest cover (with a canopy cover greater than 30%) is estimated to have been reduced by 24-28% over the last three generations (based on data between 2000 and 2020) (Global Forest Watch [2021], using Hansen et al. [2013] and methods disclosed therein). Much of this forest cover loss has been the result of complete clearance and conversion to oil palm plantations. Although this species does occur in oil palm (e.g. Yahya et al. 2020), it does so at lower densities than in primary forest (see Kemp et al. 2009 vs Yahya et al. 2020). It does, however, appear tolerant of fragmentation and can persists in heavily degraded areas, including urban parks (eBird 2021). For these reasons, population reductions are suspected to be at a lower rate than that of forest loss: suspected here to be 15-20%. This species is also affected by capture for the pet trade (Nijman & Nekaris 2017, Siriwat et al. 2020). Using assigned probability curves according to expert opinion on trade desirability in conjunction with accessibility to determine likely rates of population loss over the next three generations (they used a previous value of 34.8 years), Symes et al. (2018) estimated loss from hunting amounted to 16.5%, but this analysis had no term to account for reproduction and the species remains comparatively rare in market surveys in most of its range (Nijman & Nekaris 2017) with no indication the species is getting more desirable. Adjusting this rate for the current three-generation period and acknowledging that the species still appears rare in markets, hunting is suspected to be causing declines of 5-10%. Accumulating threats, the species is suspected to have declined 20-29% over the past three generations; this rate of decline is suspected to continue at the same rate into the future.

This species comprises two subspecies. The nominate occurs from Tenasserim, southernmost Myanmar, through Peninsular Malaysia to Sumatra, Indonesia, including Bangka Island. Subspecies strepitans occurs on Borneo, Java and Bali (König et al. 2008, Eaton et al. 2021).

The species inhabits lowland evergreen forest and semi-evergreen forest, and forest edge and clearings; also secondary growth, mature oil palm plantations and well-wooded gardens (Holt et al. 2020). Data suggest it is also capable of persisting in relatively small, isolated urban park fragments (eBird 2021). This species appears to be commoner in primary habitats: of 14 records from Malaysian Borneo, 10 were in primary forest, 1 was in secondary forest and 3 in fallow agricultural land (Puan et al. 2015), however this study did not account for survey effort in each of these habitats [although other species did not show such differences between habitat types]. Across 90 sampling points in three oil palm small holdings (53 km²) in Peninsular Malaysia, B. sumatranus was detected only once, vs 435 times for Strix seloputo (Yahya et al. 2020), while in primary forest in Peninsular Thailand, B. sumatranus was detected at densities of 0.47-1.85/km² (Kemp et al. 2009). It occurs mostly in the lowlands to 600 m, locally to 1,000 m; in the Malay Peninsula, recorded exceptionally to 1,400 m (Wells 1999) and in West Java to 1,600 m (König et al. 2008), up to 1,862 m in Malaysian Borneo (Puan et al. 2015) and rarely to 2,000 m elsewhere in Indonesia (Eaton et al. 2021). The species forages on a wide variety of prey including insects and small mammals, especially rodents, and snakes and small birds (König et al. 2008, Foley et al. 2013); takes larger prey too, including an observation of feeding on a young macaque (Li 2010).

The principal threat to this species is habitat loss with forest cover in its range reducing by 24-28% over the last three generations (22 years; Bird et al. 2020) (Global Forest Watch [2021] using Hansen et al. [2013] data and methods disclosed therein). Although it is capable of surviving in degraded habitats, including plantations and urban parks, densities appear to much greater in mature forest and very low in oil palm plantations (which has been the chief driver of lowland Sundaic forest loss). This species is also impacted by hunting, both for the pet trade (Nijman and Nekaris 2017) and, to a lesser extent, for food (Shepherd and Shepherd 2009).

Conservation Actions Underway
CITES Appendix II. No targeted conservation actions are known for this species although it occurs in a number of protected areas.

Conservation Actions Proposed
Conduct repeated surveys in areas within and surrounding its range to determine the full extent of distribution and measure rates of population decline or range contraction. Conduct ecological studies to improve understanding of its precise habitat requirements and densities in respective tolerance of secondary habitats. Campaign for the protection of remaining tracts of lowland broadleaved forest throughout the Sundaic region. Continue to monitor rates of forest loss using remote sensing data. Enforce legislation that protects this species from hunting and trade.

Text account compilers
Berryman, A., Ekstrom, J., Butchart, S.

---

Recommended citation
BirdLife International (2024) Species factsheet: Barred Eagle-owl Bubo sumatranus. Downloaded from https://datazone.birdlife.org/species/factsheet/barred-eagle-owl-bubo-sumatranus 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.