Current view: Data table and detailed info
Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
IUCN Red List criteria met and history
Red List criteria met
Red List history
Migratory status |
not a migrant |
Forest dependency |
medium |
Land-mass type |
|
Average mass |
- |
Population justification: The population size of this species has never been formally estimated, although it is described as 'uncommon' by Eaton et al. (2021). Citizen science data (eBird 2023) suggest it is found in most forest blocks that have been searched and is considered here to be a widespread bird on Sumba. Remote sensing data indicate that c.2,000 km2 of forest remains on Sumba (per Global Forest Watch 2023), and most of this is suspected to be occupied given this species' apparent tolerance of degradation (Olsen et al. 2009, Eaton et al. 2021). Few robust densities for Ninox owls are available, although Jakosalem et al. (2013) recorded densities of up to 20 mature individuals/km2 for Ninox rumseyi of Cebu. However, these data were based on home ranges from satellite-tracking that the authors acknowledged yielded territory sizes that were probably too small due to the short time the birds were followed for. The estimated home ranges were, for example, up to ten times smaller than that of Ninox boobook sensu stricto (Olsen et al. 2011). Inferring a density of 5-15 mature individuals/km2, and an occupancy of 50-80%, the population size of Ninox rudolfi is inferred to be 5,000-24,000 mature individuals, with a precautionary best estimate of 5,000-15,000.
Trend justification: The only identified threat to this species is habitat loss and degradation. In the three generations (17.3 years; Bird et al. 2020) to 2022, forest cover on Sumba declined by c.6% (Global Forest Watch 2023, based on data from Hansen et al. [2013] and methods disclosed therein). This species is tolerant of edge habitat and degraded forest (Olsen et al. 2009) and therefore may not be declining directly in line with forest cover loss. Alternatively, rates of population decline may be slightly faster than forest cover loss alone, on the basis that the species requires larger trees for nesting. Given these uncertainties, the population is tentatively suspected to be declining at a rate of 1-9% over three generations.
Country/territory distribution
Important Bird and Biodiversity Areas (IBA)
Recommended citation
BirdLife International (2024) Species factsheet: Sumba Boobook Ninox rudolfi. Downloaded from
https://datazone.birdlife.org/species/factsheet/sumba-boobook-ninox-rudolfi 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.