Introduction
Bonaparte’s Nightjar (Caprimulgus concretus), also known as the Sunda Nightjar, is a poorly known nocturnal bird of the Sundaic region. It belongs to the nightjar family, Caprimulgidae, and is restricted mainly to lowland forests on Borneo, Sumatra and Belitung. Its cryptic plumage, nocturnal activity and preference for dense forest make it difficult to study and observe.
The species was described by Charles Lucien Bonaparte in 1850. Despite its scientific name and common name being well established, many aspects of its ecology, population size and breeding biology remain incompletely documented.
Physical Description
Bonaparte’s Nightjar is a medium-sized nightjar with predominantly dark brown plumage. The upperparts are patterned with blackish, brown and buff markings, while the underparts are barred in brown and buff tones. This colouration provides effective camouflage among leaf litter, branches and shaded forest vegetation.
A distinct white patch on the lower throat is an important feature. The wings are rounded, and the tail is relatively short and slightly forked. Males may show conspicuous white markings on the outer tail feathers, although sexing birds in the field can be difficult, particularly in poor light or when the tail is folded.
Reliable published measurements for total body length are limited. Museum specimens have recorded wing lengths of approximately 161–166 mm, but the species should not be identified by size alone. No well-established age-related plumage sequence is currently available for field use.
Range and Habitat
Bonaparte’s Nightjar is endemic to the Sundaic region. Confirmed records come from:
- Borneo, including parts of Brunei, Malaysia and Indonesian Kalimantan.
- Sumatra, Indonesia.
- Belitung, an island east of Sumatra.
It is primarily a lowland forest species. It has been recorded in lowland dipterocarp forest, peat-swamp forest, forest clearings, kerangas or heath forest, secondary growth and some forest-edge habitats. Most records are from low elevations, although an isolated record from approximately 900 metres requires caution and does not indicate that the species is generally montane.
The distribution is unevenly documented, with many large areas of suitable habitat remaining poorly surveyed. It is not known to be migratory, and available evidence suggests that it is a resident of its forest range.
Behaviour and Diet
Bonaparte’s Nightjar is nocturnal and is likely to be most active from dusk through the night and again before dawn. It is generally encountered singly or in low numbers rather than in large groups. During daylight, it may remain motionless on a branch or among ground vegetation, relying on its cryptic plumage for concealment.
Available observations suggest that it feeds on flying insects and may also sally from an upright perch to take prey in or near the surrounding vegetation. Some records indicate that it remains within woodland rather than regularly foraging over open ground. The available evidence is limited, so the relative importance of aerial hawking, sallying and gleaning is not yet clear.
Its voice is described as unusual and potentially distinctive. Vocal activity may provide a useful way to survey the species, but the call has not been documented well enough to support a simple general description for field identification.
Breeding information was formerly extremely scarce. A historical museum record reported a nest containing one egg on the ground in scrub jungle. More recent work in Brunei provided the first detailed description of the nest, egg and nestling. The species lays its egg directly on the ground or on a very simple ground nest in suitable forest-floor habitat. Incubation periods, fledging times and the relative roles of the two adults remain insufficiently documented.
Identification Tips
When identifying a possible Bonaparte’s Nightjar, look for the following combination of features:
- A medium-sized nightjar in dark brown, buff and blackish plumage.
- A noticeable white patch on the lower throat.
- Strongly barred brown-and-buff underparts.
- White markings on the outer tail feathers, especially in males.
- Occurrence in lowland forest, peat-swamp forest, heath forest or nearby dense secondary vegetation on Borneo, Sumatra or Belitung.
- A bird flushed from the forest floor or seen perched quietly at low or moderate height during daylight.
The species is easily overlooked because its plumage blends with bark, dead leaves and shadowed vegetation. Identification should be based on several characters together, as lighting, posture and the visibility of the throat and tail markings can vary considerably.
Conservation Status
Bonaparte’s Nightjar is assessed as Vulnerable on the IUCN Red List categories. The assessment reflects its restricted lowland-forest distribution and the continuing loss and degradation of suitable habitat across the Sundaic region.
The principal threats are deforestation, forest fragmentation, logging, conversion of forest for agriculture and plantations, drainage or alteration of peat-swamp forests, and infrastructure development. Because the species is poorly known and often difficult to detect, its population size and precise trend remain uncertain. Nevertheless, continuing declines are inferred from the rapid reduction of lowland forest within its range.
Important conservation measures include protecting remaining lowland and peat-swamp forests, maintaining habitat connections between forest blocks, improving management of existing reserves and conducting further surveys using both visual and acoustic methods. Better information on breeding success, population density, habitat use and responses to secondary forest would help guide conservation planning.
Frequently Asked Questions
Where does Bonaparte’s Nightjar live?
It occurs on Borneo, Sumatra and Belitung. The species is mainly associated with lowland forest, including dipterocarp, peat-swamp and kerangas or heath forest.
Is Bonaparte’s Nightjar migratory?
There is no reliable evidence that it undertakes regular long-distance migration. It is generally treated as a resident species within its Sundaic range.
What does Bonaparte’s Nightjar eat?
It is an insectivorous nightjar that feeds mainly on flying insects and other invertebrates. Observations suggest that it may hunt from a perch within forest vegetation.
How can Bonaparte’s Nightjar be identified?
Key features include dark cryptic plumage, a white lower-throat patch, barred brown-and-buff underparts and, particularly in males, white markings on the outer tail feathers. Its lowland-forest habitat and unusual call can also assist identification.
Where does Bonaparte’s Nightjar nest?
The species nests on the ground or in a very simple ground nest. A nest has been documented in scrub jungle, and a later study described the nest, egg and nestling from kerangas forest in Brunei.
Why is Bonaparte’s Nightjar threatened?
Its main threat is the loss and fragmentation of lowland forest through logging, agricultural conversion, plantations, peatland drainage and infrastructure development. Its naturally restricted range increases its vulnerability to these changes.
References
- BirdLife International. 2001. Threatened Birds of Asia: The BirdLife International Red Data Book. Volume 2. BirdLife International, Cambridge. Species account: Sunda Nightjar Caprimulgus concretus. Available at: https://birdlifedata.blob.core.windows.net/red-data-books/caprconc.pdf (accessed 8 September 2026).
- Brooks, D. M., Adul & Cheyne, S. M. 2018. A camera-trap survey of avifauna in a Bornean peat-swamp forest. The Wilson Journal of Ornithology 130(4): 969–980. https://doi.org/10.1676/17-00047
- Gill, F., Donsker, D. & Rasmussen, P., eds. 2026. IOC World Bird List, version 15.2. International Ornithologists’ Union. Available at: https://www.worldbirdnames.org/new/ioc-lists/ (accessed 8 September 2026).
- Grafe, U., Jeffrey, J. & Wong, J. S. H. 2022. First description of the nest, egg and nestling of Bonaparte’s Nightjar Caprimulgus concretus from a kerangas forest in Brunei. Journal of Asian Ornithology 38: 125–128. Available through the Oriental Bird Club: https://www.orientalbirdclub.org/jao-38 (accessed 8 September 2026).
- Naturalis Biodiversity Center. 2023. Type specimens of non-passerines in Naturalis Biodiversity Center, including Caprimulgus concretus Bonaparte, 1850. Biodiversity Data Journal. Available through the Naturalis specimen record and associated publication data (accessed 8 September 2026).
- World Bird Names. 2023. Bonaparte’s Nightjar, Caprimulgus concretus. World Bird Names, Caprimulgidae. Available at: https://www.worldbirdnames.com/caprimulgiformes/caprimulgidae (accessed 8 September 2026).
Related posts
