Sunda Frogmouth Batrachostomus cornutus Scientific name definitions

23–28 cm. Plumage coloration very variable, and much confusion in the literature over how much of the variation is attributable to sexual dichromatism and how much to polymorphism. Adult male has broad pale supercilium, pale collar across upper mantle, and prominent whitish oval spots on scapulars; underparts mottled, belly and flanks paler with dark spots and bars. Occurs as two colour morphs, with intermediates: black-and-white morph has upperparts blackish, finely freckled and vermiculated with whitish to pale buff; brown-and-buff morph similar in general pattern, but blackish areas are replaced by brown and the whitish areas replaced by pale buff. Adult female varies from rather plain, with much deep rufous on upperparts and rufous on underparts, to so heavily freckled as to resemble brown-and-buff morph of male. The only juvenile specimen seen, a female, had soft-textured plumage and coloration closest to that of most rufous variants of adult female, but with paler upperparts and underparts. Both sexes are similar to smaller and shorter-tailed B. affinis, especially female, which is almost inseparable, although the present species’ white markings on the underparts are typically more extensive, and B. affinis generally shows some dark barring on belly (hard to see) and lacks blackish plumage tones. Also sympatric is B. poliolophus, which too is smaller and paler, with more boldly spotted upperparts. Race longicaudatus averages longer-tailed and thinner-billed, with less contrast in plumage.

Editor's Note: This article requires further editing work to merge existing content into the appropriate Subspecies sections. Please bear with us while this update takes place.

Formerly considered conspecific with B. javensis by some, but combined study of vocalizations and museum specimens (1 Marshall, J. T. (1978). Systematics of Smaller Asian Night Birds Based on Voice. Ornithological Monographs 25. American Ornithologists’ Union, Washington, DC, USA. Close ) supported earlier suggestions that the two should be regarded as separate species. Recent suggestion that population of a small Batrachostomus frogmouth in Palawan (W Philippines) may be a race of present species is without foundation, as Palawan birds constitute race chaseni of B. javensis. Since 2005, several observations (and photographs) of a frogmouth on island of Siberut, off W Sumatra, perhaps involve this species or B. javensis, or alternatively an undescribed taxon (2 Verbelen, P. and DeMeulemeester, B. (2012). Field observations of an unidentified frogmouth Batrachostomus on Siberut, Mentawai Islands, West Sumatra, Indonesia. Birding ASIA 17: 106–108. Close , 3 Rombang, W.M. (2009). First photographic evidence and a breeding record of a frogmouth on Siberut, Mentawai islands, West Sumatra. Kukila 14: 28–29. Close ); further study required. Has been suggested that birds from Borneo and Sumatra display consistent morphological differences that should be recognized taxonomically (4 Eaton, J. A., B. van Balen, N. W. Brickle, and F. E. Rheindt (2016). Birds of the Indonesian Archipelago: Greater Sundas and Wallacea. Lynx Edicions, Barcelona, Spain. Close ). Two subspecies recognized.

Possibly present also on Siberut, off W Sumatra (2 Verbelen, P. and DeMeulemeester, B. (2012). Field observations of an unidentified frogmouth Batrachostomus on Siberut, Mentawai Islands, West Sumatra, Indonesia. Birding ASIA 17: 106–108. Close , 3 Rombang, W.M. (2009). First photographic evidence and a breeding record of a frogmouth on Siberut, Mentawai islands, West Sumatra. Kukila 14: 28–29. Close ).

Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

One stomach contained beetle (Coleoptera) remains, while large katydids (Holochlora sp.), an American cockroach (Periplaneta americana), a cricket (Gymnogryllus sp.), a grasshopper (Orthoptera) and praying mantis (Hierodula sp.) have been observed being fed to young (5 Syahputra and Iqbal, M. (2016). Breeding records of Sunda Frogmouth Batrachostomus cornutus on Bangka island, Sumatra, Indonesia, with information on parenting behaviour and diet. BirdingASIA. 26: 32–38. Close ). No further information available.

Territorial song, presumably of female, a descending series of “qwaa” units, like “caw” of Large-billed Crow (Corvus macrorhynchos), typically giving 11 notes in 8·5 seconds; also heard is a slightly descending, drawn-out whistle  lasting c. 2 seconds that tails-off and has been rendered “peeeyoo”, as well as a series of laughing “waa” notes uttered in swift succession, typically five notes in c. 2·2 seconds (4 Eaton, J. A., B. van Balen, N. W. Brickle, and F. E. Rheindt (2016). Birds of the Indonesian Archipelago: Greater Sundas and Wallacea. Lynx Edicions, Barcelona, Spain. Close ). Vocalizations of race longicaudatus unknown, but require study in light of suggestion that this taxon might be more closely related to B. javensis (4 Eaton, J. A., B. van Balen, N. W. Brickle, and F. E. Rheindt (2016). Birds of the Indonesian Archipelago: Greater Sundas and Wallacea. Lynx Edicions, Barcelona, Spain. Close ).

Poorly known; on Sumatra an egg in Jun and a nestling in early May, while on offshore Bangka I, adults with chicks observed in late Jun, late Sept and mid Mar, and possible nestbuilding seen in early Feb, indicating that the species potentially breeds year-round there (5 Syahputra and Iqbal, M. (2016). Breeding records of Sunda Frogmouth Batrachostomus cornutus on Bangka island, Sumatra, Indonesia, with information on parenting behaviour and diet. BirdingASIA. 26: 32–38. Close ); with respect to Borneo, in Brunei, a half-grown nestling in late May, in Sabah a smaller young also in May (6 Cleere, N. (2010). Nightjars, Potoos, Frogmouths, Oilbird and Owlet-nightjars of the World. WildGuides, Old Basing, UK. Close ), and in Sarawak a three-week-old young in mid Feb (7 Holyoak, D. T. (2001). Nightjars and Their Allies: The Caprimulgiformes. Oxford University Press, Oxford, UK. Close ). Nest is a small rounded structure with shallow cup, built mainly of down, moss and small bark fragments, c. 7 cm in diameter and just 1 cm deep (7 Holyoak, D. T. (2001). Nightjars and Their Allies: The Caprimulgiformes. Oxford University Press, Oxford, UK. Close ), placed on horizontal branch, in one case of an exotic Mimosa tree, c. 1·5 m above ground (7 Holyoak, D. T. (2001). Nightjars and Their Allies: The Caprimulgiformes. Oxford University Press, Oxford, UK. Close ), another at 6 m in an Acacia and a third was c. 3 m high on a Mangifera indica (5 Syahputra and Iqbal, M. (2016). Breeding records of Sunda Frogmouth Batrachostomus cornutus on Bangka island, Sumatra, Indonesia, with information on parenting behaviour and diet. BirdingASIA. 26: 32–38. Close ). Clutch one white egg, size 25–31·9 mm × 18·8–21·2 mm (7 Holyoak, D. T. (2001). Nightjars and Their Allies: The Caprimulgiformes. Oxford University Press, Oxford, UK. Close ); incubation and fledging periods, and roles of sexes in caring for eggs and young, largely undescribed, but recent observations on Bangka I suggest that male incubates by day and female at night, probably changing over around dawn and dusk.

Not globally threatened (Least Concern). Little recent information on its status, but probably the commonest of the smaller Batrachostomus on Borneo, where known from Tanjung Puting National Park, in Kalimantan Tengah (8 Mann, C. F. (2008). The Birds of Borneo: An Annotated Checklist. B.O.U. Checklist 23. British Ornithologists’ Union, and British Ornithologists’ Club, Peterborough. Close ); only recent records from Sumatra are several from Way Kambas National Park. A population of frogmouths, tentatively ascribed to this species, was recently discovered on Mentawai Is, on Siberut. The species’ preference for second growth (even for breeding) suggests that it may be less at risk from loss of habitat than are its sympatric congeners that require primary rainforest.