70 Indian Vol. 17 No. 3 (Publ. 8 July 2021)

Vocalisation of Mountain Ducula badia and its taxonomic implications

Niranjana C & Praveen J

Niranjana C. & Praveen J. 2021. Vocalisation of Mountain Imperial Pigeon Ducula badia and its taxonomic implications. Indian BIRDS 17 (3): 70–72. Niranjana C., P.G. Program in Wildlife Biology and Conservation, National Centre for Biological Sciences-TIFR, GKVK Campus, Bellary Road, Bengaluru 560065, Karnataka, . E-mail: [email protected] [Corresponding author.] Praveen J., Villa #5, Embassy Homes, Mudavanmugal, Poojappura 695012, Thiruvananthapuram, Kerala, India. E-mail: [email protected] Manuscript received on 21 May 2021.

he Mountain Imperial Pigeon Ducula badia is a contrast set appropriately to obtain the sharpest sonograms. pigeon that occupies a wide range in the Oriental Region— Since we used a higher contrast for the measurements, the faint Tfrom the in the west to south-eastern onset of every note may have been missed in a few medium and Borneo in the east (del Hoyo et al. 2020). It comprises quality recordings, but these have hardly influenced the relative four subspecies: the nominate occurs in southern Tenasserim, values of the measurements. A single observer (NC) manually through Borneo and western Java; griseicapilla occurs from measured the maximum/minimum frequencies and start/end Nagaland up to south-eastern China, , , and time of each of the three notes. From these values, we calculated ; insignis occurs from central to Meghalaya values for eight measures: Maximum and minimum frequency and Arunachal Pradesh; and the disjunct cuprea occurs in the of the entire call, total call duration, duration of each note Western Ghats roughly southwards of Goa (del Hoyo et al. (three values), and interval duration between the three notes 2020). HBW/BirdLife International (BirdLife International 2014) (2 interval values) (Table 1). We applied Principal Component split cuprea from the other three on the basis of morphological Analysis (PCA) to identify the clusters using an R Script (prcomp and plumage differences; a stand not accepted yet by any function in stats package) and verified the results by listening to other (Dickinson & Remsen 2013; Clements et al. the recordings. 2019; Gill et al. 2021). However, del Hoyo et al. (2020) and Rasmussen & Anderton (2012) stated that the vocalisation of cuprea is poorly documented and it is unclear whether there are any unambiguous differences from the rest of the badia group. Avian taxonomy is moving strongly towards the concept of integrative taxonomy, where multiple lines of evidence including genetic, acoustic, morphological, and plumage are used to delineate species (Cicero et al. 2021). While there was a lack of Fig. 1. Typical Mountain Imperial Pigeon three-noted uk-ook ook call (ML154167051), and interval 2 acoustic data a decade ago, databases of Xeno-Canto and the measure (duration of the interval between second and third note). Recordist: Sharad Apte Macaulay Library now have a fairly comprehensive representation of vocalisations for all subspecies. We used these data sources to Results & Discussion analyze the vocalisation of this species complex. We found that a majority of cuprea vocalisations could be unanimously assigned by checking the length of the interval Methods between the second and third note (Interval2; Fig. 1), with this We downloaded all sound recordings of the Mountain Imperial interval falling in a range of 0.45–0.81s, while the rest of the Pigeon from www.xeno-canto.org and www.macaulaylibrary.org. subspecies ranged from 0.24 to 0.59s. The total duration of The most common vocalisation is the low-pitched, three-noted cuprea calls fell in the range 1.52–1.86s while the range for uk-ook ook, each note being upwardly inflected towards the the other three subspecies was 1.13–1.53s. Hence, the call end, subsequently referred to as the call (Fig. 1). Aurally, we of cuprea is audibly less hurried than that of the other three categorised the recordings by quality: High, Medium, or Low. subspecies (Fig. 2; Table 1). The PCA plot (Fig. 3) clearly shows To avoid any particular individual influencing the analysis, we cuprea calls clustering differently than those of the other three selected one call within each recording that we classified as High taxa—with the first principal component explaining 33% of the or Medium in quality. Thus we had 13 cuprea, 6 insignis, 16 total variable (loading on total duration), and second principal griseicapilla, and 8 badia samples—all assigned geographically, component explaining 24% (loading on Interval2). As the first and hence sampling a good spread of of recordings from all two components of PCA only explain 57% of the varaiation, we geographies within their ranges. We analysed the call in RavenLite investigated PC3 (15% loading on Note1 duration) and PC4 with a spectrogram window size of 2048 (as frequency variations (12% loading on interval2 again), but they did not provide any were slight and we needed higher fidelity) with brightness and different clustering for cuprea. Niranjana & Praveen: Mountain Imperial Pigeon 71

Table 1. Avarage values of the measurements for all the four subspecies Species Maximum fre- Minimum fre- Total Interval 1 (s) Interval 2 (s) Note1 Note 2 Note 3 quency (Khz) quency (Khz) duration (s) duration (s) duration (s) duration (s) badia 0.33±0.01 0.18±0.01 1.27±0.08 0.13±0.04 0.46±0.07 0.06±0.02 0.31±0.06 0.3±0.06 griseicapilla 0.33±0.02 0.19±0.02 1.33±0.08 0.16±0.02 0.41±0.09 0.06±0.03 0.35±0.07 0.35±0.05 insignis 0.35±0.01 0.18±0.02 1.38±0.03 0.18±0.05 0.42±0.05 0.07±0.03 0.33±0.03 0.39±0.06 cuprea 0.35±0.02 0.21±0.01 1.64±0.12 0.20±0.07 0.65±0.11 0.06±0.03 0.37±0.1 0.35±0.07

Fig. 2. From top to bottom: badia (ML36353), griseicapilla (ML183047), insignis (ML241888971), and cuprea (ML154167051). Recordists: Arnoud van den Berg, Roger McNeill, Sharad Apte (2) respectively

Fig. 4A,B. Box plot for total duration (A), and the second interval duration (B). Groups badia cuprea The key morphological differences of cuprea are dark (vs griseicapilla pale) iris and narrower tail band. Apart from this, cuprea also insignis has a slightly shorter wing and longer bill length, on an average, than the nearest subspecies insignis. The morphological differences are significant and consistent, positively supporting a split of cuprea from the badia group of subspecies (del Hoyo Fig. 3. PCA showing cuprea clustering differently from other races et al. 2019). The vocal analysis shows that there is a modest, 72 Indian Birds Vol. 17 No. 3 (Publ. 8 July 2021)

but consistent, difference between the call of cuprea and the Cicero, C., Mason, N. A., Jiménez, R. A., Wait, D. R., Wang-Claypool, C. Y., & Boriw, R. other races, which are much more similar to one another. This C. K., 2021. Integrative taxonomy and geographic sampling underlie successful may have taxonomic implications. The calls of pigeons are species delimitation. Ornithology 138: 1–15. DOI: https://10.1093/ornithology/ considered innate, and vocal differences have been used as a ukab009. [Accessed on 25 January 2020.] Clements, J. F., Schulenberg, T. S., Iliff, M. J., Billerman, S. M., Fredericks, T. A., Sullivan, strong argument to elevate taxa in this family to species level (Ng B. L., & Wood, C. L., 2019. The eBird/Clements Checklist of Birds of the World: et al. 2016). Species rank was given to the congeneric Nicobar v2019. Website URL: https://www.birds.cornell.edu/clementschecklist/download/. Imperial Pigeon D. nicobarica based on similar evidences (Collar [Accessed on 25 January 2020.] et al. 2020). A phylogenetic study would provide further insight Collar, N. J., Boesman, P., & Singh, P. (2020). Species rank for the Nicobar Imperial- in the taxonomic status of cuprea, but these morphological and pigeon Ducula nicobarica. Journal of the Bombay Natural History Society vocal differences would point towards a likely genetic divergence (JBNHS), 117. of this allopatric taxon. While awaiting such results, we believe del Hoyo, J., L. F. Baptista, N. Collar, P. W. Trail, G. M. Kirwan, H. M. Horblit, E. F. J. Garcia, and P. F. D. Boesman (2020). Mountain Imperial-Pigeon (Ducula badia), that cuprea can be accorded a species status. version 1.0. In Birds of the World (S. M. Billerman, B. K. Keeney, P. G. Rodewald, We recommend the English name ‘Malabar Imperial Pigeon’ and T. S. Schulenberg, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. for cuprea, as against ‘Nilgiri Imperial Pigeon’ used by BirdLife https://doi.org/10.2173/bow.moipig1.01 International, as the taxon is decidedly rare in the upper Nilgiri del Hoyo, J., Collar, N., Kirwan, G. M., & Garcia, E. F. J., 2019. Nilgiri Imperial- Plateau (Zarri & Rahmani 2005; Zarri et al. 2009) compared to pigeon (Ducula cuprea). In: Handbook of the Birds of the World Alive (J. del other wetter in the Western Ghats Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Lynx Edicions, Barcelona. Dickinson, E. C., & Remsen, J. V. J., (eds.) 2013. The Howard and Moore complete Acknowledgements checklist of the birds of the world: 1. Non-passerines. 4th ed. Eastbourne, UK: We are thankful to Pamela Rasmussen for encouraging us to take up this study.We Aves Press. Vol. 1 of 2 vols.: Pp. i–l, 1–461. are also indebted to the contributors of the recordings that were available through the Gill, F., Donsker, D., & Rasmussen, P., (Eds). 2021. IOC World List (v11.1). DOI: open platforms of Xeno-Canto and the Macaulay Library, namely, Archie J, Arnoud https://doi:10.14344/IOC.ML.10.1. [Accessed on 25 January 2020.] van den Berg, Ashwin Viswanathan, Ben F. King, Brian Sullivan, David Edwards, Ng, E. Y., Eaton, J. A., Verbelen, P., Hutchinson, R. O., & Rheindt, F. E., 2016. Using David Farrow, Eveny Luis, Felix Hesse, Frank Lambert, Greg Irving, John van der bioacoustic data to test species limits in an Indo-Pacific island radiation of Woude, Josep del Hoyo, Julia Wittmann, Linda Macaulay, Mandar Bhagat, Manoj Macropygia cuckoo doves. Biological Journal of the Linnean Society 118 (4): Karingamadathil, Marc Anderson, Mark Robbins, Mathias Ritschard, Namassivayan 786–812. Lakshmanan, Nick Athanas, Pankaj Lad, Paul Fenwick, Peter Boesman, Ramit Singal, Rasmussen, P. C., & Anderton, J. C., 2012. Birds of South Asia: the Ripley guide. 2nd Roger McNeill, Sharad Apte, Susan Myers, Vivek Puliyeri, and Warren Y. Brockelman. ed. Washington, D.C. and Barcelona: Smithsonian Institution and Lynx Edicions. 2 vols. Pp. 1–378; 1–683 References Zarri, A. A., & Rahmani, A. R., 2005. Annotated avifauna of the Upper Nilgiris, Western BirdLife International. 2014. The BirdLife checklist of the birds of the world: Version Ghats, Tamil Nadu, India. Buceros 10 (1): i–iii, 1–46. 7. Website URL: http://www.birdlife.org/datazone/userfiles/file/Species/ Zarri, A. A., Rahmani, A. R., & Senthilmurugan, B., 2009. Birds of the Upper Nilgiris Taxonomy/BirdLife_Checklist_Version_70.zip [.xls zipped 1 MB]. [Accessed on plateau, Western Ghats, India. Journal of the Bombay Natural History Society 105 25 May 2021.] (2): 181–195 (2008).

With the compliments of G.B.K. Charitable Trust Unit No. T-6C, Phoenix House, S. B. Marg, Lower Parel, Mumbai 400013, India.

In Memoriam Paul Johnsgard (1932 – 2021)