Data Zone
Justification of Red List category
This species is confined to lowland Sundaic forest which continues to be cleared rapidly to make way for agriculture, especially oil palm plantations. Over the last 16 years (three generations), it is suspected of having declined by more than 30% because of this, and such rapid rates of forest loss do not appear to be slowing. Accordingly, it is listed as Vulnerable.
Population justification
The global population size has not been quantified but is believed to be large given the range and frequency of records in suitable habitat. It is a highly forest-dependent species that has only occasionally been recorded from undisturbed forest (eBird 2022). Within its range, the rate of forest conversion to plantations, primarily oil palm, has been very rapid over the past few decades (per Global Forest Watch 2022). There are recent records from remaining forested areas across much of the range, however the extent of suitable habitat is now considerably smaller than three generations ago. Where habitat is secure the species continues to be regularly observed, although it is evidently scarce (Eaton et al. 2021, eBird 2022) and observing the species away from protected areas is becoming increasingly difficult.
In Thailand, there is only one definite record, from Nakhon Si Thammarat province (Treesucon and Limparungpatthanakij 2018). There remains a small area of suitable habitat abutting the Malaysian border (with adjacent records). However, if the species does indeed persist in Thailand, its population is likely to be very small, since this is among the best-surveyed and -watched countries within this species' range.
In Peninsular Malaysia, almost all records now come from protected areas in the north or Taman Negara National Park, although there are recent scattered records from elsewhere (MNS Bird Conservation Council 2021, eBird 2022), suggesting the species can be found in most places flat, low-lying habitat remains.
On Sumatra, the species has evidently always been scarce but occurred more widely than contemporary records suggest (see van Marle and Voous 1988). In recent years, there are confirmed records from only Way Kambas National Park. Despite ostensibly suitable habitat, and the detection of four other frogmouth species it has, perhaps surprisingly, not been recorded on the Kampar Peninsula (RER 2017, eBird 2022); while presumed to occur there, its population density in forest blocks on the island's east half must be very low. On Sumatra, the population may therefore now be relatively small.
On Borneo, the area of suitable habitat remains large (especially in Kalimantan), although this species still remains one of the most infrequently observed nightbirds across the island away from a handful of sites. Although the population size is not estimated herein, it is unlikely to be small given the extent of suitable habitat. However, determining the species' density in different habitats across its range should be a research priority.
Trend justification
Batrachostomus auritus is thought to be declining rapidly in response to extensive forest cover loss across its range. In the absence of population data, forest cover loss is used as a proxy to estimate the rate of reduction over the past three generations (16.2 years; Bird et al. 2020), however doing this accurately relies on robust knowledge of the species' distribution when forest cover was more extensive. There is, however, much uncertainty on how widespread it was on the Thai-Malay Peninsula and Sumatra historically. Under a range of mapped scenarios, forest cover loss in the species' range is thought to have reduced by 26-47% over the last three generations (Global Forest Watch 2022, based on data from Hansen et al. [2013] and methods disclosed therein). Excluding the most extreme of these scenarios (which are considered the least likely), the population is thought to have reduced by 30-45% over the past three generations. This rate is also precautionarily suspected over the next three generations, although beyond that rates of loss may slow as the percentage area of forest outside protected areas diminishes.
Batrachostomus auritus occurs very sparsely in south peninsular Thailand, where it is known from only a single definitive record; also Sabah, Sarawak and Peninsular Malaysia; Kalimantan (including the Natuna and Labuan islands) and Sumatra, Indonesia, and Brunei.
It occurs in lowland dipterocarp forest, apparently no higher than c.300 m (Eaton et al. 2021). A nest has been described from a branch fork c.4 m from the ground, from which a chick hatched in mid-March (Cheong and Li 2010).
Forest destruction in the Sundaic lowlands of Indonesia and Malaysia has been extensive, for timber and conversion to agriculture. In particular the rapid expansion of oil palm has driven the conversion of the majority of remaining lowland forest in the region. Between 2005 and 2021, tree cover was reduced in its range by 26–47% (depending on the assumptions used) (Global Forest Watch 2022, based on data from Hansen et al. [2013] and methods disclosed therein). Moreover, the impact of forest degradation will have added to rates of decline. Associated with the forest loss has been an increase in fire frequency, extent and severity, particularly during strong El Nino events (as in 1998).
Conservation Actions Underway
None specific to this species is known, but it occurs in several protected areas across its range (UNEP-WCMC and IUCN 2023).
Conservation Actions Proposed
Continue to estimate population trends by calculating rates of forest loss within its range using satellite imagery and remote sensing techniques. Protect areas of lowland forest within the species' range. Enforce restrictions on agricultural encroachment and logging within such protected areas.
Text account compilers
Berryman, A.
Contributors
Benstead, P., Bird, J., Eaton, J., Khwaja, N., Taylor, J. & Westrip, J.R.S.
Recommended citation
BirdLife International (2024) Species factsheet: Large Frogmouth Batrachostomus auritus. Downloaded from
https://datazone.birdlife.org/species/factsheet/large-frogmouth-batrachostomus-auritus 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.