A team of ornithologists from the National University of Singapore, Birdtour Asia Ltd. and the University of Queensland has described a mysterious new species of the cuckoo hawk genus. Hierococcix from Borneo, a large island shared by the Malaysian states of Sabah and Sarawak, the Indonesian state of Kalimantan and the Sultanate of Brunei.
Breeding range map Hierocopcix Boki from Sumatra and Peninsular Malaysia, Hierococcix sp. from Borneo and Hierococcyx sparveriodes. Image credit: Ayuwat Jirwatanakanok/Robert O. Hutchinson/James A. Eaton.
Hierococcix – a small genus of birds in the cuckoo family. Cuculids.
First created in 1845, the genus currently includes nine scientifically recognized species.
Commonly known as cuckoo hawks, they can be found in South, Southeast and East Asia.
“Inside the cuckoo hawk genus Hierococcix“The two tropical and subtropical Asian species form a close-knit pair,” said the lead author. Dr. Frank Rhindt from the National University of Singapore and his colleagues.
“They are variously merged into one species or recognized as two monotypic species: great cuckoo hawk (Hierococcyx sparverioides) And Boca's cuckoo-hawk or dusky cuckoo-hawk (Hierocopcix Boki)“
“These cuckoo hawks are found in forests from the Himalayas and China to Southeast Asia.”
“Hierococcyx sparverioides – a more widespread taxon that breeds widely in the mountainous tropical, subtropical and even temperate regions of mainland Asia and winters in the south.”
“Hierocopcix Boki ridges in the mountain forests of Sundaland.”
“Historically, the distinction between species Hierococcix cuckoos, like most other birds, were guided by differences in plumage,” they noted.
“However, the two species have only minor differences in plumage.”
“Since the 1990s, the taxonomy of many tropical and subtropical bird species complexes has undergone a revolution with increasing understanding of the importance of bioacoustic traits for species delimitation.”
“Species boundaries in numerous tropical and subtropical Asian bird species complexes have been redrawn based on bioacoustic data.”
In their new study, Dr. Rhindt and co-authors sought to examine the taxonomy Hierococcyx sparverioides–Hierocopcix Boki pair and discover evidence of the existence of mysterious species.
To do this, they used an integrative approach based on bioacoustic, feather and morphometric data.
They analyzed a total of 107 sound recordings of these two species, obtained from online sound libraries.
They also assessed plumage differences and morphometric traits measured from a series of museum specimens.
Their analysis revealed a separate, as yet unnamed population Hierocopcix Boki native to Borneo, who can be distinguished from other populations mainly by their unique three-syllable main song.
Given the importance of vocalizations in cuckoo taxonomy, they described this population as a new species to science: Hierocoptsix tiganada.
“The new species from Borneo is very similar to its sister species. Hierocopcix Boki from Sumatra and Peninsular Malaysia,” the researchers said.
“Visually the two species are almost identical, but the adults of the new species have a slightly grayer mantle, especially the upper part of the mantle towards the crown, resulting in a distinct lack of contrast between the gray crown and the browner dorsum seen in Hierocopcix Boki“
“The best distinguishing feature between the two species is the structure of their brain-fever song: in new species it is always three-syllable, and in new species it is always two-syllable. Hierocopcix Boki“
“Hierococcyx sparverioides differs from the new species by the same characteristics that distinguish it from Hierocopcix Boki“, they added.
“Hierococcyx sparverioides He also has a two-syllable song that causes brain fever.”
“Besides, an adult Hierococcyx sparverioides has a larger body size, is less dark gray in front of the eye, has a browner back less contrasting with the crown, and has distinct dark rufous stripes on a whitish background on the upper chest (solid rufous, no stripes in the new species).”
According to scientists, Hierocoptsix tiganada Inhabits mountain tropical forests at an altitude of more than 1000 m above sea level.
“Despite the alarming conservation status of many Southeast Asian birds that live in tropical forests, Hierocoptsix tiganada He’s probably not in any danger,” they said.
“Although Borneo's lowland tropical forests have suffered significant losses over the past three decades, much of the montane forests in central Borneo survive due to their remoteness and inaccessibility to logging companies and other extractive industries.”
“Hierocoptsix tiganada is relatively well known in three places in Sabah and one in Sarawak.”
“There are extremely few records in Kalimantan, and the species appears to be truly absent from the Meratus Mountains in South Kalimantan.”
“However, the species is likely to be ubiquitous across large areas of mountainous northern Borneo, often close to the border between Kalimantan, Sarawak and Sabah, and the lack of widespread records likely reflects poor observer coverage away from well-known birding sites.”
Hierocoptsix tiganada this is the first Hierococcix species that will be described in the 20th and 21st centuries.
“This discovery highlights the continued importance of bioacoustic research in biodiversity discovery and further enhances the biogeographic significance of Borneo,” the authors concluded.
Their paper will be published in Journal of Asian Ornithology.
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Frank E. Rhindt etc.. 2025. New mysterious species of cuckoo hawk (genus Hierococcix) from Borneo. Journal of Asian Ornithology 41:34-43
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