[Ornithology • 2025] Birds of a feather: Comprehensive Plumage Colour Analysis for A Revised Subspecies Classification of the Chestnut-winged Babbler Cyanoderma erythropterum species complex

Map of Southeast Asia showing type localities (large flag markers) and collection localities of museum specimens (small circles) for the various taxa described under Cyanoderma erythropterum and C. bicolor.

 

in Teo, Sin, Nieves et Rheindt, 2025. 

DOI: doi.org/10.1016/j.avrs.2025.100307 

Images of Babblers modified from Eaton et al. (2016).

 

ABSTRACT

Quantitative analysis of colouration is an essential tool for subspecies delimitation but has always posed a challenge in avian taxonomy. In this study on the Chestnut-winged Babbler (Cyanoderma erythropterum) species complex from tropical Southeast Asia, we made use of colour measurements taken with digital cameras and applied two methodologies—(1) the 75% subspecies rule on quantitative colourimetric variables, and (2) the CIEDE2000 colour distance method to generate phylograms, which has probably never been applied in taxonomy before. Given its large number of described subspecies, many of which have been synonymised in modern taxonomies, the species complex serves as an appropriate model to test subspecies validity. Our data indicate that one synonymised subspecies (C. e. apega), from the islands of Bangka and Belitung, requires re-instalment and recognition, whereas one widely recognised subspecies (C. e. fulviventre), from the Banyak Islands, should be synonymised. Our approach also allowed us to redraw geographic subspecies boundaries. Our work indicates that current subspecies taxonomies of many poorly known tropical species may remain error-ridden and highlights the importance and viability of large-scale taxonomic revisions targeting avian subspecies globally while incorporating quantitative colourimetric approaches.

Keywords: Chestnut-winged Babbler, Colour distance, Subspecies boundaries, Subspecies rule, Taxonomy

Map of Southeast Asia showing type localities (large flag markers) and collection localities of museum specimens (small circles) for the various taxa described under Cyanoderma erythropterum and C. bicolor.
Flag markers are positioned precisely at type localities except in the case of C. e. pyrrhophaeum, whose type locality is ill-defined as ‘Sumatra’. Subspecies that are widely synonymised are shown with the same colour (both in font and type locality flag) as the taxon under which they are usually subsumed. Underlined names refer to subspecies that have widely been accepted prior to this study. Red dots indicate the localities of specimens from the Lee Kong Chian Natural History Museum (Singapore), while light-blue dots indicate the localities of specimens from other museums. Black stippled lines represent subspecies boundaries widely followed prior to this study, while yellow stippled lines represent revised subspecies boundaries proposed in this study. The dark-grey shaded area in Borneo reflects remaining uncertainty around the boundary between C. b. bicolor and C. b. rufum.

Images of babblers modified from Eaton et al. (2016).

Conclusions: 

Our results validate the current synonymisation of neocarum and sordidum with erythropterum, and of pellum with pyrrhophaeum. Our data also show that a widely recognised subspecies, fulviventre from the Banyak Islands, is indistinct in plumage and should be synonymised with pyrrhophaeum. Subspecies apega from the Bangka and Belitung islands is widely synonymised in modern taxonomies, but emerged as distinct in its crown colouration, exhibiting a pattern that would render it intermediate between C. erythropterum and C. bicolor. We advocate a resurrection of this subspecies, and confirm its placement within C. erythropterum on the basis of vocal data. Our examination of specimens indicates that the subspecies boundary between rufum and bicolor is much further south than widely assumed, although we do not rule out the possibility that rufum may form part of a cline of crown colour across Borneo.

The following is our proposed subspecies taxonomy for the Chestnut-winged Babbler (Cyanoderma erythropterum) complex:

● Cyanoderma erythropterum (Blyth, 1842): 

Chestnut-winged Babbler

○ C. e. erythropterum (Blyth, 1842) – Type locality: Singapore

■ Range: Thai-Malay Peninsula, Singapore, Riau Islands, Natuna Islands

■ Synonyms: sordidum Baker, 1917; neocarum Oberholser, 1932

○ C. e. pyrrhophaeum (Hartlaub, 1844) – Type locality: “Malacca and Sumatra” (here restricted to Sumatra, as Malacca was a trading hub)

■ Range: Sumatra, Batu and Banyak Islands

■ Synonyms: pellum Oberholser, 1912; eripellum Oberholser, 1922; fulviventre Richmond, 1903

■ Main diagnosis: Grey breast darker than erythropterum

○ C. e. apega Oberholser, 1922 – Type locality: Tanjong Tedong, Bangka Island

■ Range: Bangka Island and Belitung Island

■ Main diagnosis: Incomplete chestnut crown with front half being slate grey unlike complete chestnut crown in erythropterum and pyrrhophaeum

● Cyanoderma bicolor (Blyth, 1865): 

Bicoloured Babbler

○ C. b. bicolor (Blyth, 1865) – Type locality: Labuan (Malaysian Borneo)

■ Range: Northern and central Borneo, Banggi Island

○ C. b. rufum (Chasen & Kloss, 1927) – Type locality: Sampit, south coast of Kalimantan

■ Range: Southern Borneo, likely found only across the Central Kalimantan Depression

■ Main diagnosis: Rufous colouration extending to the nape, and even to some extent to the crown, unlike the grey colouration observed in bicolor

Shen Han Teo, Yong Chee Keita Sin, Mayjean Marie Ines Nieves and Frank E. Rheindt. 2025. Birds of a feather: Comprehensive Plumage Colour Analysis for A Revised Subspecies Classification of the Chestnut-winged Babbler (Cyanoderma erythropterum) species complex. Avian Research. In Press, 100307. DOI: doi.org/10.1016/j.avrs.2025.100307  [4 October 2025]

[Ornithology • 2006] Liocichla bugunorum | Bugun Liocichla • A New Species of Liocichla (Aves:Timaliidae) from Eaglenest Wildlife Sanctuary, Arunachal Pradesh, India

Pic. 1. The holotype of Bugun Liocichla Liocichla bugunorum sp nov.
It was photographed on 25.v.2006 at Lama Camp just outside the boundaries of Eaglenest Wildlife Sanctuary, Arunachal Pradesh, India. The overall colour of the bird is olive which tends to look greener in the shade (see Pic. 6) and neutral grey in bright light (a camera flash for instance). This is probably a male bird.

Abstract

This paper describes a new bird species of the genus Liocichla discovered near Eaglenest Wildlife Sanctuary in western Arunachal Pradesh, India. While the taxon most closely resembles L. omeiensis, an endemic of China, the many points of difference in plumage, size and vocalisations indicate a new species. The known population is very small and only three (breeding?) pairs responded to song play back in May 2006. The plumage and the vocalisations are distinctive and therefore the paucity of records suggests a small and highly localized population.

Bugun Liocichla Liocichla bugunorum sp. nov.

Taxonomic status

Evaluating the relative status of taxa is not easy (Helbig et al. 2002), especially when all other congeners are allopatric. Visually and aurally, L. bugunorum is most similar to L. omeiensis but there are many points of difference between them: in vocalisations, ten features of plumage, and size (Table 1). While future surveys may extend their ranges towards each other the balance of probability of finding intermediate populations, showing a cline in all the above differences is low. Furthermore, L. bugunorum differs from L. omeiensis and from L. steerii in its plumage as much as the latter differ between themselves. L. omeiensis was elevated from subspecies (of L. steerii) to species (Cheng 1987). These factors make a strong case for assigning specific rank to the Eaglenest taxon.

 On the lack of a full specimen

Given the very small known population, I felt it would be inappropriate to collect a specimen, especially as that would have affected one of only three known (breeding?) pairs. So only some feathers which had worked loose (after the photographs were taken) were collected as type material. Should the census planned for next season indicate a larger population, steps will be taken to obtain a full specimen after seeking permission from the appropriate authorities.

Etymology: All observations of this taxon, except the first, were carried out during field work under the Eaglenest Biodiversity Project (Athreya 2005, 2006). Local community participation and development have been the cornerstones of our conservation efforts there and Mr Indi Glow of the Bugun tribe has played a very critical role throughout the project. Furthermore, all sightings of the taxon except one have been in Bugun community forest. It gives me great pleasure to acknowledge the contribution of Mr. Indi Glow and others by naming the new taxon after their Bugun tribe. The word Bugun (both ‘u’ rhyme with “put”) is a masculine term used by the community to refer to themselves. It is believed to mean “people of the valley = valley dwellers” but the etymology is uncertain and its origins may lie in another language. The specific name

bugunorum [= (Liocichla) of the Buguns] is the invariable genitive plural of the latinised noun Bugunus.

Athreya, Ramana. 2006. A New Species of Liocichla (Aves:Timaliidae) from Eaglenest Wildlife Sanctuary, Arunachal Pradesh, India. Indian Birds. 2(4): 82-94.

http://www.indianbirds.in/pdfs/IB.2.4.Liocichla.pdf

A. Townsend Peterson and Monica Pape. 2006. Potential geographic distribution of the Bugun Liocichla Liocichla bugunorum, a poorly-known species from north-eastern India. Indian Birds. 2 (6): 146–149.

http://www.bio-nica.info/biblioteca/Peterson2006DistributionLiocichla.pdf

[Ornithology • 2013] Emei Shan Liocichla Liocichla omeiensis: Population, Behavior and Conservation | endemic to mountain ranges in south-central Sichuan & extreme north-east Yunnan, China

  

Abstract 

Endemic to China, the Emei Shan Liocichla (Liocichla omeiensis) is considered globally vulnerable by the IUCN because of its small, declining population and fragmented range. The species has been recorded in only a few mountainous forests in south-central Sichuan and in the extreme northeast of Yunnan Province. We summarized the basic eco-biology information on its habitat, breeding, winter habits and behavior, voice, population status, research and conservation.

Keywords: Emei Shan Liocichla, habitat, breeding, population, conservation

Yiqiang FU, Simon D. DOWELL and Zhengwang ZHANG. 2013. Emei Shan Liocichla: Population, Behavior and Conservation. Chinese Birds. 4(3): 260–264. DOI dx.doi.org/10.5122/cbirds.2013.0023