Summary of Morphometric Sexing of Chestnut-winged Babbler, Black-capped Babbler, Short-tailed Babbler and Little Spiderhunter in Peninsular Malaysia

Articles by Chong Leong Puan1,2,3, Wei Lun Ng4, Christina S.Y. Yong5 and Abdl Jalil Norehan1
1Faculty of Forestry, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia
2Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia
3Biodiversity Unit, Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia
4School of Life Sciences, Sun Yat-sen University Guangzhou, 510275 Guangdong, China
5Department of Biology, Faculty of Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia


Babblers are the primary understory insectivorous birds in the forests of Southeast Asia, whereas Spiderhunters (Nectariniidae) are nectarivorous and arthropod hunters, most of which are sexually monomorphic. Babblers are characterised by their soft and loose plumage, often short distance flyers with relatively short rounded wings (Jeyarajasingam, 2012). Spiderhunters on the other hand are characterised by their long decurved bill. Unlike the confamilial sunbirds that are often sexually dimorphic with males being relatively more colourful than females, it may be difficult to differentiate the sexes of spiderhunters unless through careful examination of their body size and pectoral tufts (Cheke et al., 2001). The study focuses on 4 common species of birds being Chestnut-winged Babbler (Cyanoderma erythropterum), Black-capped Babbler (Pellorneum capistratum), Short-tailed Babbler (Pellorneum malaccense), and Little Spiderhunter (Arachnothera longirostra), that were sampled using mist-nets in Bintang Hijau Forest Reserve, Sungai Lalang Forest Reserve, Panti Forest Reserve, and Shah Alam Botanical Garden.

The purpose of the studies were to investigate the morphological differences between sexes of the subjected species. Therefore, morphological measurements were obtained for the total body, head, wing chord, tarsus, tail and bill lengths using a calliper and a ruler, in mm. Weight was measured using a spring balance, in g. Blood samples were collected by pricking the brachial vein with a sterile 27-gauge needle (Davis 2005), and samples were mixed with 100% ethanol and stored at 4℃. All the birds were released after having their measurements and blood sample taken. Genomic DNA from blood samples was extracted and analysed to determine the sex molecularly where males are homogametic sex by having 2 Z chromosomes, while females are heterogametic sex having one Z chromosome and W chromosome.

Figure 1 Measurement of (A) wing, (B) tail, (C) tarsus, (D) bill, and (E) head lengths


The total sample size was of 23 little spiderhunters with 11 males and 12 females, 31 chesnut-winged babblers with 19 males and 12 females, 31 short-tailed babblers with 22 males and 9 females and 22 black-capped babblers with 20 males and 2 females. Visually, 8 male little spiderhunters were successfully identified through the presence of pectoral tufts. By using Discriminant Function Analysis (DFA) on the morphological measurements of each species, significant differences were found between the sexes of each species.

For the Little Spiderhunter, the results have shown that 5 morphological parameters can be used, where male birds have longer bodies, wings, tails, bills and head length.  Although the pectoral tufts may be a good indication of sex i.e. adult male, but this characteristic may not be observed in juveniles and subadults that do not have visible orange-yellow gape flange (Wells, 2010). Hence, for the respective 2 age range, wing and tail lengths may be useful to identify the sexes. For the Chestnut-winged Babbler, the male birds have longer head and wing lengths. For the Short-tailed Babbler, the male birds also have longer head and tail lengths. Whereas for the Black-capped Babbler, the wing and total body lengths of the males were comparatively longer, although only 2 females were caught.


Table 2

Morphometric measurements from little spiderhunter and results of Mann-Whitney U-test

Measurements Male (n = 11) Female (n = 12) Z p
± SE 95% CI ± SE 95% CI
Head length (mm) 60.09 ± 3.62 51.51-69.49 52.75 ± 0.54 51.57-53.93 -3.721 <0.001
Bill length (mm) 38.27 ± 0.88 35.92-40.08 34.25 ± 0.54 33.07-35.43 -3.382 0.001
Wing length (mm) 68.18 ± 0.33 67.33-68.67 60.17 ± 0.49 59.09-61.25 -4.097 <0.001
Tail length (mm) 45.18 ± 0.55 43.80-45.80 38.71 ± 0.59 37.42-40.00 -4.101 <0.001
Tarsus length (mm) 20.20 ± 0.13 19.90-20.50 19.25 ± 0.46 18.23-20.27 -2.458 0.014
Total body length (mm) 152.27 ± 2.49 145.80-158.20 142.50 ± 1.98 138.14-146.86 -2.994 0.003
Weight (g) 13.18 ± 0.52 11.90-14.50 12.75 ± 1.72 8.97-16.53 -1.686 0.092


In the studies, a set of morphometric characters that are useful for direct sex determination in the field are identified for the 3 babbler species and 1 spiderhunter species. Since the sexing of birds is important in behavioural and ecological studies, this study provided an inexpensive, rapid, less invasive and accurate way for future sex determination of the 4 bird species. Therefore, despite these species are often described in field guides as sexually monomorphic, it is still possible and rather accurately sexed by referring to morphological measurements as the study results suggested. Other than aiding in sexual differentiation, such study is also useful to highlight the importance of collecting morphological traits in the field and its potential in answering a bigger ecological question, e.g. pertaining to functional morphology, trophic diversification and resource partitioning of sympatric species, which are fundamental factors in driving biotic community assembly in the tropics. With specialised feeding structure, the little spiderhunter has great potential as a focal species for the study of complex ecological interactions in the tropics (Olsen et al., 2013). For example, since male little spiderhunters have longer bills than the females, it would be interesting to examine if differential foraging is present between the sexes, i.e. possible interactions between the birds, as pollinators, and floral anatomy (Paton & Collins, 1989; Sakai et al., 1999; Cronk & Ojeda, 2008; Sakai et. al., 2013). Such research is especially important in view of the increasing risk of losing avian pollinators around the world (Regan et al., 2015).

Note: Little Spiderhunter in Featured Image was one of the many species sighted during Wild Bird Club Malaysia’s trip to Kubah National Park, Sarawak. The full checklist is available here.

The Black-capped Babbler picture was sourced from eBird checklist which is available here. 


Summarised from:

  1. Puan C.L., Norehan A. J., Ng W.L., Yong C. S. Y. (2018). Intersexual and interspecific morphometric variations among three sympatric babbler species from Peninsular Malaysia. Malayan Nature Journal 2018, 70(1), 27-32.
  2. Puan C.L., Norehan A. J., Ng W.L., Yong C. S. Y. (2018). Morphometric Sexing of Little Spiderhunter (Arachnothera longirostra) in Peninsular Malaysia. Pertanika Journal Tropical Agricultural Science 41 (1): 333-340.


Jeyarajasingam, A. 2012. A Field Guide to the Birds of Peninsular Malaysia and Singapore, Second Edition (p. 449). Oxford: Oxford University Press.

Myers, S. 2009. A Field Guide to the Birds of Borneo. London: New Holland.

Cheke, R. A., Mann, C. F., &Allen, R. (2001). Sunbirds: A Guide to the Sunbirds, Flowerpeckers, Spiderhunters and Sugarbirds of the World. (p. 384). London: Christopher Helm Publishers.

Davis, A. K. (2005). Effect of handling time and repeated sampling on avian white blood cell counts. Journal of Field Ornithology, 76(4), 334-338.

Sakai, S., Kato, M., & Inoue, T. (1999). Three pollination guilds and variation in floral characteristics of Bornean gingers (Zingiberaceae and Costaceae). American Journal of Botany, 86(5), 646–658.

Sakai, S., Kawakita, A., Ooi, K., & Inoue, T. (2013). Variation in the strength of association among pollination systems and floral traits: evolutionary changes in the floral traits of Bornean gingers (Zingiberaceae). American Journal of Botany, 100(3) 546-555.

Paton, D. C., & Collins, B. G. (1989). Bills and tongues of nectar-feeding birds: A review of morphology, function and performance, with intercontinental comparisons. Australian Journal of Ecology, 14(4), 473-506.

Cronk, Q., & Ojeda, I. (2008). Bird-pollinated flowers in an evolutionary and molecular context. Journal of Experimental Botany, 59(4), 715-727

Regan, E. C., Santini, L., Ingwall-King, L., Hoffmann, M., Rondinini, C., Symes, A., … & Butchart, S. H. M. (2015). Global trends in the status of bird and mammal pollinators. Conservation Letters, 8(6), 397-403.

Photo Credit: Little Spiderhunter (YL Yeo), Black-capped Babbler (Choy Wai Mun)