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

Justification of Red List category
This species has a moderately large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km² combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over three generations). The population size is unknown, but is not suspected to be sufficiently small to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
The population size of this species has not been quantified, although it is described as fairly common (B. Harris in litt. 2016, Eaton et al. 2021). The total area of suitable habitat, spanning more than 40,000 km², is large, and eBird (2022) data suggest the species does not occur at a particularly low density. Consequently, the population size is likely to be much larger than 10,000 mature individuals.

Trend justification
The population is suspected to be declining slowly due to habitat loss at the lower elevations of its range. In the three generations (10.7 years; Bird et al. 2020) to 2022, forest cover loss in its range was 2-4% (Global Forest Watch 2022, based on Hansen et al. [2013] and methods disclosed therein), and this is thought to have had an equivalent (hence minimal) impact on the population. Trapping for the songbird trade has also been identified as a threat to this species. However, the species has only very rarely (and in small numbers) appeared on physical market survey inventories (Chng et al. 2016, 2018), and using a web-scraping tool to mine data from online marketplace platforms, Okarda et al. (2022) found no D. sumatranus among c.105,000 listings, although they did detected 162 "Dicrurus sp.", at least some of which may refer to this species. Consequently, although trapping may cause local losses at the most accessible locations, it is unlikely to be causing significant reductions in global population size. Evaluating all the data available, the population is suspected of declining at a past and future rate of 1-9% over three generations. With much of the range lying in protected areas, there is little prospect of the rate of declining substantially worsening in the near-future.

Dicrurus sumatranus is restricted to Sumatra (with race viridinitens on the Mentawai Islands), Indonesia (BirdLife International 2001).

This species occurs in lowland, hill and lower montane forest and tall secondary forest, typically between 700 and 1,600 m on Sumatra (Harris et al. 2017, Eaton et al. 2021) and at all elevations on the Mentawai Islands.

The loss of lowland forest in Sumatra has been extensive as a result of both regulated and illegal logging, as well as conversion to agriculture. This is thought to have impacted this species at lower elevations in its range. In the three generations (10.7 years; Bird et al. 2020) to 2022, forest cover loss in its range was 2-4% (Global Forest Watch 2022, based on Hansen et al. [2013] and methods disclosed therein). Trapping for the songbird trade has also been identified as a threat to this species. However, the species has only very rarely (and in small numbers) appeared on physical market survey inventories (Chng et al. 2016, 2018), and using a web-scraping tool to mine data from online marketplace platforms, Okarda et al. (2022) found no D. sumatranus among c.105,000 listings, although they did detect 162 "Dicrurus sp.", at least some of which may refer to this species. Consequently, although trapping may cause local losses at the most accessible locations, it is unlikely to be causing significant reductions in global population size.

Conservation Actions Underway
None is specifically known. Much of its range lies in protected areas (UNEP-WCMC and IUCN 2022).

Conservation Actions Proposed
Continue to monitor habitat trends using remote sensing data. Undertake surveys to determine the species' population size, as well as its tolerance of logging and habitat degradation. Ensure effective enforcement of Sumatran protected areas and national laws.

Text account compilers
Berryman, A.

Contributors
Benstead, P., Gilroy, J., Harris, B., Martin, R. & Taylor, J.

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Recommended citation
BirdLife International (2024) Species factsheet: Sumatran Drongo Dicrurus sumatranus. Downloaded from https://datazone.birdlife.org/species/factsheet/sumatran-drongo-dicrurus-sumatranus 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.