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A distance sampling survey of the Critically Endangered Straw-headed Bulbul Pycnonotus zeylanicus in Singapore

Published online by Cambridge University Press:  16 November 2020

WEN XUAN CHIOK Open the ORCID record for WEN XUAN CHIOK [Opens in a new window] ,
ELIZE Y. X. NG ,
QIAN TANG ,
JESSICA G. H. LEE  and
FRANK E. RHEINDT
WEN XUAN CHIOK*
Affiliation:
Department of Biological Sciences, National University of Singapore, 16 Science Drive 4, Singapore 117558, Singapore.
ELIZE Y. X. NG
Affiliation:
Department of Biological Sciences, National University of Singapore, 16 Science Drive 4, Singapore 117558, Singapore.
QIAN TANG
Affiliation:
Department of Biological Sciences, National University of Singapore, 16 Science Drive 4, Singapore 117558, Singapore.
JESSICA G. H. LEE
Affiliation:
Wildlife Reserves Singapore, 80 Mandai Lake Rd, Singapore 729826, Singapore.
FRANK E. RHEINDT
Affiliation:
Department of Biological Sciences, National University of Singapore, 16 Science Drive 4, Singapore 117558, Singapore.
*
*Author for correspondence; e-mail: chiokwenxuan@gmail.com
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Summary

The Straw-headed Bulbul Pycnonotus zeylanicus is one of South-East Asia’s most threatened songbirds due to relentless demand for the regional cage-bird trade. The species was recently uplisted from ‘Endangered’ to ‘Critically Endangered’ only two years after its previous uplisting. Intriguingly, populations in highly urbanised Singapore appear relatively secure. However, the last Singaporean density estimates, derived from traditional census methods, were obtained nearly two decades ago in 2001. A recent population estimate in 2016 was derived from the census work in 2001 coupled with relative abundance indices from population trends. We thus performed systematic field surveys using the distance sampling method, estimating 573 ± 185 individuals nation-wide, with a break-down of 217 ± 81 on the main island of Singapore and 356 ± 104 birds on the satellite of Pulau Ubin. Taken together, the total population estimate reported here comprises 22.9–57.3% of the global wild population, underscoring the importance of Singapore as a stronghold for the species. In spite of its apparently secure status in Singapore, the species remains susceptible to local and foreign trapping pressures. Based on our assessment, we propose a number of local and regional conservation measures to ensure the continued survival of populations in Singapore.

Keywords

songbird crisispopulation assessmentSouth-East Asiapasserinepoint count
Type
Research Article
Information
Bird Conservation International , Volume 31 , Issue 3 , September 2021 , pp. 468 - 480
Copyright
© The Author(s), 2020. Published by Cambridge University Press on behalf of BirdLife International

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References

Akaike, H. (1973) Information theory and an extension of the maximum likelihood principle. Pp. 267–281 in Petrov, B. N. and Csàki, F., eds. Second International Symposium on Information Theory. Budapest: Akademiai Kiàdo.Google Scholar
Barlow, J., França, F., Gardner, T. A., Hicks, C. C., Lennox, G. D., Berenguer, E., Castello, L., Economo, E. P., Ferreira, J., Guénard, B., Gontijo Leal, C., Isaac, V., Lees, A. C., Parr, C. L., Wilson, S. K., Young, P. J. and Graham, N. A. J. (2018) The future of hyperdiverse tropical ecosystems. Nature 559: 517–526.CrossRefGoogle ScholarPubMed
Barraclough, R. K. (2000) Distance sampling: A discussion document produced for the Department of Conservation, New Zealand. Science and Research Internal Report 175.Google Scholar
Bart, J., Droege, S., Geissler, P., Peterjohn, B. and Ralph, C.J. (2004) Density estimation in wildlife surveys. Wildl, Soc. Bull. 32: 1242–1247.CrossRefGoogle Scholar
Bergin, D., Chng, S. C. L., Eaton, J. A. and Shepherd, C. R. (2018) The final straw? An overview of Straw-headed Bulbul Pycnonotus zeylanicus trade in Indonesia. Bird Conserv. Internatn., 28: 126–132.CrossRefGoogle Scholar
Bibby, C. J., Burgess, N. D. and Hill, D. A. (2000) Bird census techniques. 2nd Edition. London, UK: Elsevier.Google Scholar
BirdLife International (2001) Threatened birds of Asia: The BirdLife International Red Data Book. Cambridge, UK: BirdLife International.Google Scholar
BirdLife International (2018) Species factsheet: Pycnonotus zeylanicus. http://datazone.birdlife.org/species/factsheet/straw-headed-bulbul-pycnonotus-zeylanicus (Accessed 18 December 2018).Google Scholar
Bombaci, S. P. and Pejchar, L. (2019) Using paired acoustic sampling to enhance population monitoring of New Zealand’s forest birds. New Zealand J. Ecol. 43: 1–11.Google Scholar
Brickle, N. W., Eaton, J. A., and Rheindt, F. E. (2010) A rapid bird survey of the Menyapa mountains, East Kalimantan, Indonesia. Forktail 26: 31–41.Google Scholar
Buckland, S. T., Anderson, D. R., Burnham, K. P., Laake, J. L., Borchers, D. L. and Thomas, L. (2001) Introduction to distance sampling. New York, USA: Oxford University Press.Google Scholar
Buckland, S. T., Marsden, S. J. and Green, R. E. (2008) Estimating bird abundance: Making methods work. Bird Conserv. Internatn., 81: 91–108.CrossRefGoogle Scholar
Buckland, S. T., Anderson, D. R., Burnham, K. P., and Laake, J. L. (2012) Distance sampling: estimating abundance of biological populations. WHEREFFS Springer Science and Business Media.Google Scholar
Cahill, A. J., Walker, J. S. and Marsden, S. J. (2006) Recovery within a population of the Critically Endangered citron-crested cockatoo Cacatua sulphurea citrinocristata in Indonesia after 10 years of international trade control. Oryx 40: 161–167.CrossRefGoogle Scholar
Camp, R. J., Pratt, T. K., Marshall, A. P., Amidon, F. and Williams, L. L. (2009) Recent status and trends of the land bird avifauna on Saipan, Mariana Islands, with emphasis on the endangered Nightingale Reed-warbler Acrocephalus luscinia . Bird Conserv. Internatn. 19: 323–337.CrossRefGoogle Scholar
Ceia, R. S., Ramos, J. A., Heleno, R. H., Hilton, G. M. and Marques, T. A. (2011) Status assessment of the critically endangered Azores bullfinch Pyrrhula murina . Bird Conserv. Internatn. 21: 477–489.CrossRefGoogle Scholar
Challender, D. W. S. and MacMillan, D. C. (2014) Poaching is more than an enforcement problem. Conserv. Lett. 7: 484–494.CrossRefGoogle Scholar
Chiok, W. X. (2019) Status assessment of three traded songbirds in Singapore. Unpublished thesis. Department of Biological Sciences, National University of Singapore.Google Scholar
Chiok, W. X., Miller, A. E., Pang, S. E. H., Eaton, J. A., Rao, M. and Rheindt, F. E. (2019) Regional and local extirpation of a formerly common Sundaic passerine, the Straw-headed Bulbul Pycnonotus zeylanicus . Forktail 35: 3–11.Google Scholar
Chng, S. C. L., Lee, J. G. H. and Shepherd, C. R. (2016) The conservation status, legal protection and assessment of the trade in Straw-headed Bulbuls Pycnonotus zeylanicus in Singapore. TRAFFIC Bull. 28: 49–52.Google Scholar
Chng, S. C. L., Eaton, J. A. and Shepherd, C. R. (2018) In the market for extinction: birds for sale at selected outlets in Sumatra. TRAFFIC Bull. 30: 15–22.Google Scholar
Chng, S. C. L., Eaton, J. A., Krishnasamy, K., Shepherd, C. R. and Nijman, V. (2015) In the market for extinction: An inventory of Jakarta’s bird markets. Petaling Jaya, Selangor, Malaysia: TRAFFIC Southeast Asia.Google Scholar
Cooney, R., Roe, D., Dublin, H., Phelps, J., Wilkie, D., Keane, A., Travers, H., Skinner, D., Challender, D. W., Allan, J. R. and Biggs, D. (2017) From poachers to protectors: Engaging local communities in solutions to illegal wildlife trade. Conserv. Lett. 10: 367–374.CrossRefGoogle Scholar
Corlett, R. T. (1992) The ecological transformation of Singapore, 1819–1990. J. Biogeogr. 411–420.CrossRefGoogle Scholar
Davison, G. W., Ng, P. K. and Ho, H. C. (2008) The Singapore Red Data Book: Threatened plants and animals of Singapore. Singapore: Nature Society.Google Scholar
Duckworth, J. W., Batters, G., Belant, J. L., Bennett, E. L., Brunner, J., Burton, J., Challender, D. W. S., Cowling, V., Duplaix, N., Harris, J. D. and Hedges, S. (2012) Why South-East Asia should be the world’s priority for averting imminent species extinctions, and a call to join a developing cross-institutional programme to tackle this urgent issue. Sapiens 5: 76–95.Google Scholar
Eaton, J. A., Shepherd, C. R., Rheindt, F. E., Harris, J. B. C., Balen, S. B. Van, Wilcove, D. S. and Collar, N. J. (2015) Trade-driven extinctions and near-extinctions of avian taxa in Sundaic Indonesia. Forktail 31: 1–12.Google Scholar
Eaton, J. A., van Balen, B., Brickle, N and Rheindt, F. E. (2016) Birds of the Indonesian Archipelago. Barcelona: Lynx Edicions.Google Scholar
Eaton, J., Leupen, B. and Krishnasamy, K. (2017) Songsters of Singapore: An overview of the bird species in Singapore pet shops. Petaling Jaya, Selangor, Malaysia: TRAFFIC Southeast Asia.Google Scholar
ESRI (2015) ArcGIS Release 10.4. Redlands, CA, USA: Environmental Systems Research Institute.Google Scholar
Farmer, R. G., Leonard, M. L. and Horn, A. G. (2012) Observer effects and avian-call-count survey quality: rare-species biases and overconfidence. The Auk 129: 76–86.Google Scholar
Fischer, J. H., Boyd, N. S., Maruly, A., Van der Kaaden, A., Husson, S. J. and Sihite, J. (2016) An inventory of the avifauna of the Bukit Batikap Protection Forest, Central Kalimantan, Indonesia. Forktail 32: 26–35.Google Scholar
Fishpool, L., Tobias, J. and Sharpe, C.J. (2018) Straw-headed Bulbul (Pycnonotus zeylanicus). In del Hoyo, J., Elliott, A., Sargatal, J., Christie, D. A. and de Juana, E., eds. Handbook of the birds of the world alive. Barcelona: Lynx Edicions.Google Scholar
Gaw, L. Y. F., Yee, A. T. K. and Richards, D. R. (2019) A high-resolution map of Singapore’s terrestrial ecosystems. Data 4: 116.CrossRefGoogle Scholar
Google (2018) Google Earth Pro desktop, version 7.3.2. Google. Retrieved from: https://earth.google.com/web/Google Scholar
Government of Singapore (2017) Master Plan 2014 Region Boundary (Web). https://data.gov.sg/dataset/master-plan-2014-region-boundary-web (Accessed 27 December 2018).Google Scholar
Gregory, R. D., Gibbons, D. W. and Donald, P. F. (2004) Bird census and survey techniques. Pp. 17–55 in Sutherland, W. J., Newton, I. and Green, R. E., eds. Bird ecology and conservation: A handbook of techniques. Cambridge, UK: Cambridge University Press.CrossRefGoogle Scholar
Harris, J. B. C., Green, J. M., Prawiradilaga, D. M., Giam, X., Hikmatullah, D., Putra, C. A. and Wilcove, D. S. (2015) Using market data and expert opinion to identify overexploited species in the wild bird trade. Biol. Conserv. 187: 51–60.CrossRefGoogle Scholar
Harris, J. B. C., Tingley, M. W., Hua, F., Yong, D. L., Adeney, J. M., Lee, T. M., Marthy, W., Prawiradilaga, D. M., Sekercioglu, C. H., Winarni, N. and Wilcove, D. S. (2017) Measuring the impact of the pet trade on Indonesian birds. Conserv. Biol. 31 394–405.CrossRefGoogle ScholarPubMed
Hilborn, R., Arcese, P., Borner, M., Hando, J., Hopcraft, G., Loibooki, M., Mduma, S. and Sinclair, A. R. E. (2006) Effective enforcement in a conservation area. Science 314(5803): 1266–1266.CrossRefGoogle Scholar
Ho, H. C. (2001) The Straw-headed Bulbul in Pulau Ubin: its breeding population, distribution and species’ habitat requirements with recommendations for conservation. Unpublished thesis. University of East Anglia, UK.Google Scholar
Hong, J. (2018) Feeding of wild animals should be banned, say most Singaporeans in survey. The Straits Times, Singapore. https://www.straitstimes.com/singapore/feeding-of-wild-animals-should-be-banned-say-most-singaporeans (Accessed 4 January 2019).Google Scholar
Indenbaum, R. A. (2018) Viet Nam Online: A rapid assessment of e-commerce wildlife trade in Viet Nam 2017. Cambridge, UK: TRAFFIC International.Google Scholar
IUCN (2001) IUCN Red List categories and criteria: Version 3.1. Gland, Switzerland and Cambridge, UK: IUCN Species Survival Commission.Google Scholar
Janssen, J. and Shepherd, C. R. (2018) Challenges in documenting trade in non CITES-listed species: A case study on crocodile skinks (Tribolonotus spp.). J. Asia-Pacific Biodiv. 11: 476–481.CrossRefGoogle Scholar
Janssen, J. and Leupen, B. T. C. (2019) Traded under the radar: poor documentation of trade in nationally-protected non-CITES species can cause fraudulent trade to go undetected. Biodiv. Conserv. 28: 2797–2804.CrossRefGoogle Scholar
Krishnasamy, K. and Stoner, S. (2016) Trading faces: A rapid assessment on the use of Facebook to trade wildlife in Peninsular Malaysia. Petaling Jaya, Selangor, Malaysia: TRAFFIC Southeast Asia.Google Scholar
Lanctot, R. B., Hartman, A., Oring, L. W. and Morrison, R. I. G. (2008) Response to Farmer (2008): Limitations of statistically derived population estimates, and suggestions for deriving national population estimates for shorebirds. Auk 125: 983–985.CrossRefGoogle Scholar
Lee, D. C. and Marsden, S. J. (2008) Adjusting count period strategies to improve the accuracy of forest bird abundance estimates from point transect distance sampling surveys. Ibis 150: 315–325.CrossRefGoogle Scholar
Lee, J. G. H., Chng, S. C. L. and Eaton, J. A. (2016) Conservation strategy for Southeast Asian songbirds in trade. Recommendations from the first Asian Songbird Trade Crisis Summit 2015 held in Jurong Bird Park, Singapore, 27–29 September 2015. Singapore: Wildlife Reserves Singapore and TRAFFIC Southeast Asia.Google Scholar
Leupen, B. T. C, Krishnasamy, K., Shepherd, C. R., Chng, S. C., Bergin, D., Eaton, J. A., Yukin, D. A., Koh, S. P. H., Miller, A., Nekaris, K. A. I., Nijman, V., Saaban, S. and Imron, M. A. (2018) Trade in White-rumped Shamas Kittacincla malabarica demands strong national and international responses. Forktail 34: 1–8.Google Scholar
Lim, K. C. and Lim, K. S. (2009) State of Singapore’s wild birds and bird habitats: A review of the annual bird census, 1996–2005. Singapore: Nature Society (Singapore).Google Scholar
Lim, K. C. and Yong, D. L. (2013) Recent trends of national threatened birds in Singapore. Pp. 71-92 in Proceedings of Nature Society, Singapore’s Conference on ‘Nature Conservation for a Sustainable Singapore’ – 16th October 2011. Google Scholar
Lim, K. S. (2009) The avifauna of Singapore. Singapore: Nature Society (Singapore).Google Scholar
Lim, K. S. (2016) Report on the 31st Annual Bird Census. Nature Society (Singapore). https://www.nss.org.sg/report/f246e330-9ABC%202016%20report.pdf (Accessed 13 July 2019).Google Scholar
Marsden, S. J. (1999) Estimation of parrot and hornbill densities using a point count distance sampling method. Ibis 141: 377–390.Google Scholar
Martin, R. O., Senni, C. and D’Cruze, N. C. (2018) Trade in wild-sourced African grey parrots: Insights via social media. Global Ecol. Conserv. 15: e00429.CrossRefGoogle Scholar
Maxwell, S. L., Fuller, R. A., Brooks, T. M. and Watson, J. E. (2016) Biodiversity: The ravages of guns, nets and bulldozers. Nature 536(7615): 143–145.CrossRefGoogle ScholarPubMed
Mittermeier, R. A., Robles Gil, P., Hoffmann, M., Pilgrim, J., Brooks, T., Mittermeier, C. G., Lamoreux, J. and da Fonseca, G. A. B. (2004) Hotspots revisited: Earth’s biologically richest and most endangered ecoregions. Mexico City, Mexico: CEMEX.Google Scholar
Myers, N. (2003) Biodiversity hotspots revisited. Bioscience 53: 916–917.Google Scholar
Myers, N., Mittermeier, R. A., Mittermeier, C. G., da Fonseca, G. A. and Kent, J. (2000) Biodiversity hotspots for conservation priorities. Nature 403(6772): 853.CrossRefGoogle ScholarPubMed
Nash, S. V. (1993) Sold for a song: The trade in Southeast Asian non-CITES birds. Cambridge, UK: TRAFFIC International.Google Scholar
Board, National Parks (2018) Pulau Ubin and Chek Jawa. Retrieved from: https://www.nparks.gov.sg/gardens-parks-and-nature/parks-and-nature-reserves/pulau-ubin-and-chek-jawa (Accessed 10 November 2018)Google Scholar
Ng, E. Y. X., Garg, K., Low, G., Chattopadhyay, B., Oh, R. R. Y., Lee, J. G. H. and Rheindt, F. E. (2017) Conservation genomics identifies impact of trade in a threatened songbird. Biol. Conserv. 214: 101–108.CrossRefGoogle Scholar
Nijman, V. (2010) An overview of international wildlife trade from Southeast Asia. Biodiv. Conserv. 19: 1101–1114.CrossRefGoogle Scholar
Nijman, V., Langgeng, A., Birot, H., Imron, M. A. and Nekaris, K. A. I. (2018) Wildlife trade, captive breeding and the imminent extinction of a songbird. Global Ecol. Conserv. 15: e00425.CrossRefGoogle Scholar
Phassaraudomsak, M. and Krishnasamy, K. (2018) Trading faces: A rapid assessment on the use of Facebook to trade in wildlife in Thailand. Petaling Jaya, Selangor, Malaysia: TRAFFIC Southeast Asia.Google Scholar
Quek, X. H. (2018) Status of poaching in Singapore: an investigation of its occurrence, diversity and distribution from Dec 2014 to Jan 2018. Unpublished thesis. Department of Biological Sciences, National University of Singapore.Google Scholar
Quinten, M. C., Waltert, M., Syamsuri, F. and Hodges, J. K. (2010) Peat swamp forest supports high primate densities on Siberut Island, Sumatra, Indonesia. Oryx 44: 147–151.CrossRefGoogle Scholar
R Core Team (2018) R: A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing. URL https://www.R-project.org/.Google Scholar
Rentschlar, K. A., Miller, A. E., Lauck, K. S., Rodiansyah, M., Bobby, Muflihati, and Kartikawati, (2018) A silent morning: The songbird trade in Kalimantan, Indonesia. Trop. Conserv. Sci., 11: 1–10.Google Scholar
Rivera, M. F. F., Bertuol, P., Simal, F. and Rusk, B. L. (2015) Distance sampling survey and abundance estimation of the critically endangered Grenada Dove (Leptotila wellsi). The Condor 117: 87–93.CrossRefGoogle Scholar
Robson, C. (2015) Birds of South-East Asia : Concise edition. London, UK: Bloomsbury Publishing.Google Scholar
Ruette, S., Stahl, P. and Albaret, M. (2003) Applying distance-sampling methods to spotlight counts of red foxes. J. Appl. Ecol. 40: 32–43.CrossRefGoogle Scholar
Shepherd, C. R., Shepherd, L. A. and Foley, K-E (2013) Straw-headed Bulbul Pycnonotus zeylanicus: legal protection and enforcement action in Malaysia. BirdingASIA 19: 92–94.Google Scholar
Shepherd, C. R., Nijman, V., Krishnasamy, K., Eaton, J. A. and Chng, S. C. L. (2016) Illegal trade pushing the Critically Endangered Black-winged Myna Acridotheres melanopterus towards imminent extinction. Bird Conserv. Internatn. 26: 147–153.CrossRefGoogle Scholar
Sim, F. (2018) Strong support for tougher wildlife protection laws in Singapore: Survey. Singapore: Channel News Asia. https://www.channelnewsasia.com/news/singapore/wildlife-protection-laws-in-singapore-louis-ng-10620890 (Accessed 5 January 2019).Google Scholar
Sin, Y. C. K., Jain, A., Lim, G., Tan, T., Yong, D. L.. (2019) Straw-headed Bulbul conservation planning workshop report. Singapore: Nature Society Singapore.Google Scholar
Singapore Land Authority (2018) Total land area of Singapore. Singapore Land Authority. https://data.gov.sg/dataset/total-land-area-of-singapore (Accessed 2 December 2018).Google Scholar
Sodhi, N. S., Koh, L. P., Brook, B. W. and Ng, P. K. (2004) Southeast Asian biodiversity: an impending disaster. Trends Ecol. Evol. 19: 654–660.CrossRefGoogle Scholar
Sodhi, N. S., Posa, M. R. C., Lee, T. M., Bickford, D., Koh, L. P. and Brook, B. W. (2010) The state and conservation of Southeast Asian biodiversity. Biodiv. Conserv. 19: 317–328.CrossRefGoogle Scholar
Subedi, T. R., Virani, M. Z., Gurung, S., Buij, R., Baral, H. S., Buechley, E. R., Anadón, J. D. and Sah, S. A. (2018) Estimation of population density of Bearded Vultures using line-transect distance sampling and identification of perceived threats in the Annapurna Himalaya range of Nepal. J. Raptor Res. 52: 443–454.CrossRefGoogle Scholar
Sung, Y. H. and Fong, J. J. (2018) Assessing consumer trends and illegal activity by monitoring the online wildlife trade. Biol. Conserv. 227: 219–225.CrossRefGoogle Scholar
Sy, E. Y. (2018) Trading faces: Utilisation of Facebook to trade live reptiles in the Philippines. Petaling Jaya, Selangor, Malaysia: TRAFFIC Southeast Asia.Google Scholar
Symes, W. S., Edwards, D. P., Miettinen, J., Rheindt, F. E. and Carrasco, L. R. (2018) Combined impacts of deforestation and wildlife trade on tropical biodiversity are severely underestimated. Nature Communic. 9: 4052.CrossRefGoogle ScholarPubMed
Tan, A. (2017) Singapore wildlife faces poaching threat. Singapore: The Straits Times. https://www.straitstimes.com/singapore/environment/spore-wildlife-faces-poaching-threat (Accessed 20 March 2019).Google Scholar
Tan, T. G. S. (2001) Population distribution of Straw-headed Bulbul Pycnonotus zeylanicus in Singapore and strategies for conservation. Unpublished thesis. University College London, UK.Google Scholar
Tang, G. S. Y., Sadanandan, K. R. and Rheindt, F. E. (2016) Population genetics of the olive‐winged bulbul (Pycnonotus plumosus) in a tropical urban‐fragmented landscape. Ecol. Evol. 6: 78–90.CrossRefGoogle Scholar
van Balen, S. (1999) Birds on fragmented islands: persistence in the forests of Java and Bali. Trop. Resour. Manage. Papers 30.Google Scholar
Wells, D. R. (2006) The birds of the Thai-Malay Peninsula: Passerines, Volume 2. London, UK: Helm, A and C. Black Publishers.Google Scholar
Yee, A. T. K., Corlett, R. T., Liew, S. C. and Tan, H. T. W. (2011) The vegetation of Singapore―an updated map. Gardens’ Bull. Singapore 63: 205–212.Google Scholar
Yee, A. T. K., Chong, K. Y., Neo, L. and Tan, H. T. W. (2016) Updating the classification system for the secondary forests of Singapore. Raffles Bull. Zool. 32: 11–21.Google Scholar
Yong, D. L., Seng Lim, K., Chuah Lim, K., Tan, T., Teo, S. and Chew, H. H. (2017) Significance of the globally threatened Straw-headed Bulbul Pycnonotus zeylanicus populations in Singapore: a last straw for the species? Bird Conserv . Internatn. 28: 133–144.Google Scholar
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