The Penan Hawk-cuckoo (Hierococcyx tiganada) is a newly described species from Borneo, formally named in a 2025 paper. Its clearest distinction from the related Dark, or Bock’s, Hawk-cuckoo is its song: the Bornean bird’s common “brainfever” motif has three elements, while related populations generally give two.
What is the newly discovered cuckoo species in Borneo?
The Penan Hawk-cuckoo is a montane hawk-cuckoo that had previously been treated as part of Bock’s (Dark) Hawk-cuckoo, Hierococcyx bocki. In 2025, Frank E. Rheindt, Gabriel G.K. Teo, James A. Eaton and Elize Y.X. Ng formally described the Bornean population as Hierococcyx tiganada, using evidence from vocalizations, plumage and museum measurements. The authors wrote: “The analysis unearthed a distinct, hitherto unnamed population of H. bocki residing on Borneo.” Read the 2025 paper in the Journal of Asian Ornithology.
What does the Penan Hawk-cuckoo sound like?
Its characteristic “brainfever” call has a three-element motif—a sequence of three vocal elements—rather than the two-element motif generally given by related H. bocki populations in Sumatra and Peninsular Malaysia. The distinction concerns the structure of the common call, not simply a claim that the bird has a louder or more melodious voice.
The authors analyzed 107 sound recordings assembled from Xeno-canto, the Macaulay Sound Library, the Avian Vocalization Center and the Internet Bird Collection. After excluding trills, they used 85 recordings for the common “brainfever” call analysis: 48 representing H. sparverioides and 37 representing H. bocki. Of the latter, 28 were from Borneo and nine from the rest of the species’ Sundaic range. The stable vocal difference, considered alongside plumage and morphometrics, supported recognizing the Bornean birds as a cryptic species: one difficult to distinguish by appearance alone.
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Where does it live?
The Penan Hawk-cuckoo is a Bornean montane bird. BirdGuides’ account of the authors’ findings says it is thought to occur mainly in montane rainforest above about 1,000 metres, with records from three broad areas in Sabah and one in Sarawak. Sparse records from Kalimantan may reflect limited observer coverage, so the known distribution should not be taken as a complete map of the species’ range. BirdGuides’ summary of the species.
How can it be distinguished from Dark Hawk-cuckoo?
The song is the most useful distinction described in the paper. Adults of the two are visually very similar; Bornean birds are described as having a somewhat greyer mantle, especially toward the crown. That color difference is not dependable in immature and subadult birds, so appearance alone may not settle an identification.
| Feature | Penan Hawk-cuckoo | Dark (Bock’s) Hawk-cuckoo |
|---|---|---|
| Common “brainfever” motif | Three elements | Generally two elements in related populations from Sumatra and Peninsular Malaysia |
| Range discussed in the paper | Borneo | Sumatra and Peninsular Malaysia; the Bornean population was formerly included here |
| Elevation and habitat | Mainly montane rainforest above about 1,000 m, according to the authors’ view as summarized by BirdGuides | Not stated in the cited material for this comparison |
| Adult mantle | Somewhat greyer, especially toward the crown | Relatively less grey in the comparison described by the paper |
| Visual identification of young birds | Grey-mantle distinction is unreliable in immature and subadult birds | Not reliably separated from Penan Hawk-cuckoo by that distinction when the other bird is immature or subadult |
The scientific description also anchors the name to a museum specimen: holotype ZRC 3.7896, a male collected at Kiau, Mount Kinabalu, Sabah, on 9 April 1929, now held at Singapore’s Lee Kong Chian Natural History Museum.
Why was it named only in 2025?
The population had been flagged earlier under the English name Penan Hawk-cuckoo. James Eaton and Frank Rheindt proposed that name in the 2016 field guide Birds of the Indonesian Archipelago: Greater Sundas and Wallacea; the 2025 paper supplied the formal scientific name Hierococcyx tiganada. The species is therefore newly described scientifically, not necessarily newly encountered by observers.
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The sources cited here do not provide a formal IUCN category. BirdGuides reports the authors’ provisional view that the species is probably not threatened, while noting that its full distribution remains imperfectly documented. That is a preliminary assessment, not a formal conservation listing.
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