Monthly Archives: September 2021

Singapore Bird Report – August 2021

by Geoff Lim & Isabelle Lee,
and Tan Gim Cheong (ed.)

Residents continued to breed, and migrants started to make their way from their northern breeding grounds to Singapore in August; while most sightings of migrants were of shorebirds, migratory songbirds have also begun to arrive.

Central Catchment Nature Reserve – CCNR

CW Babbler, 018021, Geoff Lim

Chestnut-winged Babbler at Thomson Nature Park on 1 Aug 2021 by Geoff Lim.

Forest species continue to be observed within and along the tracks leading into the Central Catchment Nature Reserve.  The presence of species such as a Thick-billed Green Pigeon, Treron curvirostra, a Chestnut-bellied Malkoha, Phaenicophaeus sumatranus, a Short-tailed Babbler, Pellorneum malaccense, and a pair of Blue-winged Leafbird, Chloropsis cochinchinensis, were noted along Rifle Range Link on 29 August 2021 by Wai Heng Lua, who also spotted a Crested Honey Buzzard, Pernis ptilorhynchus. Other birds seen within the CCNR were one Red-crowned Barbet, Megalaima rafflesii, and three Asian Red-eyed Bulbul, Pycnonotus brunneus, spotted by Ester Gerber on 31 Aug 2021.

The tracks around Mandai, such as Mandai Track 7, have proven to be good birding grounds, given its proximity to old forests such as the Nee Soon forest complex. On 1 August 2021, a Malaysian Hawk-Cuckoo, Hierococcyx fugax, was spotted by Chen RX, while on 21 August 2021, forest specialists, such as a Cream-vented Bulbul, Pycnonotus simplex, and a Chestnut-winged Babbler, Cyanoderma erythropterum, were seen by Tan Kok Hui.

CCNR fringe parks supported species such as a pair of Chestnut-winged Babbler, Cyanoderma erythropterum, on 1 August 2021 at Thomson Nature Park by Geoff Lim, a Square-tailed Drongo Cuckoo, Surniculus lugubris, of which one was seen on 2 August 2021 at Thomson Nature Park by Yip Jen Wei; while along Old Upper Thomson Road, three Brown Hawk-Owl, Ninox scutulata, were reported on 10 Aug 2021 by Tanvi DG. Over at Windsor Nature Park, a Blue-eared Kingfisher, Alcedo meninting, on 27 Aug 2021 (Yap Bao Shen), two Blue-rumped Parrot, Psittinus cyanurus, and a Blyth’s Paradise Flycatcher, Terpsiphone affinis, on 28 Aug 2021 (Fadzrun A), as well as four Long-tailed Parakeet, Psittacula longicauda, on29 Aug 2021 (Matthijs van Bevervoorde) were spotted.

For the Stork-billed Kingfisher, Pelargopsis capensis, nest at Windsor Nature Park, one of the chicks fledged on 14 August 2021 and the nest appeared empty thereafter (Samuel CWJ). The status of the other chick is not known, it could have fledged earlier when no one was around. Nothing is known about the fledging period of the Stork-billed Kingfisher (Wells, 2007). The discovery of the nest on 20 July 2021, when young with unopened eyes were being fed by the parents, tells us that the fledging period is more than 25 days.

SBKF nest, 020821, WNP, Lee Chin Pong

Stork-billed Kingfisher feeding a chick at the nest, the other chick’s bill can be seen near the top of the nest hole, Windsor Nature Park on 2 Aug 2021 by Lee Chin Pong.

At Dairy Farm Nature Park, Yeong WaiKai found the nest of a Straw-headed Bulbul, Pycnonotus zeylanicus, on 25 August 2021. At the Singapore Quarry, an Oriental Darter, Anhinga melanogaster, a Laced Woodpecker, Picus vittatus, a Rufous Woodpecker, Micropternus brachyurus, and two Rufous-tailed Tailorbird, Orthotomus sericeus, were spotted on 28 August 2021 by Wai Heng Lua.

Singapore Botanic Gardens

The Singapore Botanic Gardens continues to be a verdant ground for birds with a Blyth’s Paradise Flycatcher, Terpsiphone affinis, that had just one tail feather, at the ethnobotanical garden on 23 August 2021 (Harry Loh). Over at the Healing and Fragrant Gardens, a Banded Bay Cuckoo, Cacomantis sonneratii, was seen on 25 Aug 2021 by Chen Boon Chong while a Common Kingfisher, Alcedo atthis, and three Coconut Lorikeet, Trichoglossus haematodus, were seen on 27 Aug 2021 by Jon Garcia. Meanwhile, on the same day, a migratory Tiger Shrike, Lanius tigrinus, was spotted by Norhafiani A Majid within the garden grounds.

Central Singapore

A single Asian Palm Swift, Cypsiurus balasiensis, was seen at Ang Mo Kio Avenue 1 on 14 August 2021 by A. Fadzrun A.

Northern Singapore

RC Sunbird, 060821, SBWR, SCC

Ruby-cheeked Sunbird seen on 6 August 2021 at SBWR by Sim Chip Chye.

Sungei Buloh Wetland Reserve (SBWR), the premier birding location in northern Singapore, welcomed a rare Ruby-cheeked Sunbird, Chalcoparia singalensis, on 3 August 2021 (Chen RX), 4 August 2021 (Joseph Lim), 5 August 2021 (Gan Lee Hsia), 6 August 2021 (Sim Chip Chye), and on 29 August 2021 (Bhagwant Kurade). The reserve also started to welcome various wintering shorebirds from the north. These included the two Black-tailed Godwit, Limosa limosa, on 14 August 2021 (Kwok Tuck Loong), three Pacific Golden Plover, Pluvialis fulva, five Lesser Sand Plover, Charadrius mongolus, eighty-six Whimbrel, Numenius phaeopus, thirty-five Common Redshank, Tringa totanus, and three Common Greenshank, Tringa nebularia, on 31 August 2021 (Alfred Chia).  Evergreen locals included a Great-billed Heron, Ardea sumatrana, (A. Fadzrun), a pair of Red Collared Dove, Streptopelia tranquebarica, (A. Fadzrun), and one Eastern Cattle Egret, Bubulcus coromandus, (Mike Hooper) on 21 August 2021, one Lesser Adjutant, Leptoptilos javanicus, (Ester Gerber) on26 August 2021, a pair of Copper-throated Sunbird, Leptocoma calcostetha, (Chen Boon Chong) on28 August 2021, and two Little Egret, Egretta garzetta, (Alfred Chia) on 31 August 2021.

A pair of Ashy Tailorbirds, Orthotomus ruficeps, was seen bringing food to their nest at the reserve on 6 August 2021 (Tan Gim Cheong), and Kwan Kee Ming observed that a Lineated Barbet, Psilopogon lineatus, started to build its nest there on 1 August 2021.

Over at Kranji Marsh, a Rusty-breasted Cuckoo, Cacomantis sepulcralis, was seen on 15 August 2021 by Kaeden Sim; a pair of introduced Golden-backed Weavers, Ploceus jacksoni, was building a nest on 11 August 2021 (Tan Gim Cheong); a pair of the introduced Common Waxbill, Estrilda astrild, was building a nest on 23 August 2021 (Keith Hutton); and a nest of the Malaysian Pied Fantail, Rhipidura javanica, contained two chicks (Shahrul Kamal). Another Malaysian Pied Fantail nest contained one chick, which fledged on 28 August 2021, but the fledgling fell into the water and was eaten by a large frog (Felix Wong).

Searchers found White-browed Crake, Porzana cinerea, at Neo Tiew Harvest Link on 15 Aug 2021 (Chen Boon Chong), and four Little Ringed Plover, Charadrius dubius, scurrying in the monsoon drain at Lim Chu Kang Lane 3 on 29 Aug 2021 (Daryl Yeo).  Further eastwards, an Intermediate Egret, Egretta intermedia, a House Swift, Apus nipalensis, and a Golden-bellied Gerygone, Gerygone sulphurea, were reported on 29 August 2021 by Kwok Tuck Loong. Traversing across the northern coastline, we noted the report of a single Western Osprey, Pandion haliaetus, and some Daurian Starling, Agropsar sturninus, along Yishun Dam on 21 August 2021 by Norman Wu, while at Lorong Halus Wetland, an Oriental Dollarbird, Eurystomus orientalis, was seen on 30 August 2021 by John Chin. In the heart of Sengkang, four Rose-ringed Parakeet, Psittacula krameri, and four relatively uncommon Common Myna, Acridotheres tristis, were spotted at Sengkang Riverside Park on 31 Aug 2021 by Tan Kok Hui.

Ashy Tailorbird, 060821, SBWR, TGC_6836,-Ashy-Tailorbird,-m-N-f,-960v

Ashy Tailorbirds, male on left and female on right (paler underparts), 6 August 2021 at SBWR by Tan Gim Cheong.

Eastern Singapore

On 4 August 2021, a fledgling Blue-winged Pitta, Pitta moluccensis, was spotted by Tan Gim Cheong in the understorey of the forest at Pulau Ubin, following a parent pitta; and on 27 August 2021, a fledgling of the similar-looking Mangrove Pitta, Pitta megarhyncha, was calling in the mangroves but no adult pitta came to attend to it (Francis Yap).

The idyllic island also hosted migratory shorebirds such as three Grey Plover, Pluvialis squatarola, and a Terek Sandpiper, Xenus cinereus, which were seen on 13 August 2021 by Oliver Tan, while other visitors encountered residents and local visitors such as the Black-naped Tern, Sterna sumatrana, (Mike Hooper), Black Hornbill, Anthracoceros malayanus, (Tan Hui Zhen), and Green Broadbill, Calyptomena viridis, (Tan Hui Zhen) on 22 August 2021, while an  Abbott’s Babbler, Malacocincla abbotti,  was seen on 23 August 2021 (Tan Gim Cheong), and a White-rumped Shama, Copsychus malabaricus, was seen the next day on 24 August 2021 (Max Khoo). Ubin’s eastern neighbour, Pulau Tekong, yielded a single Grey-tailed Tattler, Tringa brevipes, on 2 August 2021 (Frankie Cheong).

Pasir Ris Park yielded a Lesser Adjutant, Leptoptilos javanicus, on 20 August 2021 (Robert Teo), a Green Imperial Pigeon, Ducula aenea, on 22 August 2021 (Kwok Tuck Loong), and a Black-crowned Night Heron, Nycticorax nycticorax, on 28 August 2021 (Clarice Yan), while five Lesser Whistling Duck, Dendrocygna javanica, were spotted at Bedok Reservoir Park on 26 August 2021 (Jiah Rai).

A White-headed Munia, Lonchura maja, was seen within the grounds of Eastwood Estate on 27 Aug 2021 (Oliver Tan), while Plaintive Cuckoo, Cacomantis merulinus, and Barn Swallow, Hirundo rustica, were seen on 29 Aug 2021 along the Changi Coast Track by A. Fadzrun.

Southern Singapore

Visitors to Gardens-by-the-Bay East spotted a Pacific Reef Heron, Egretta sacra, on 15 Aug 2021 (Fermandez Francis) and seven Masked Lapwing, Vanellus miles, on 28 Aug 2021 (Andrew William). At the breakwater along Marina East Drive in late August, Pary Sivaraman counted 160 Little Terns, Sternula albifrons.

After a failed nesting last month, a pair of Malaysian Plovers, Charadrius peronii, was seen guarding an egg on 1 August 2021 but when revisited 10 days later, “they were gone” (Ko Engwee). The nesting in July failed due to a House Crow which carried off the chick (Low Chong Yang). The chick was at least 25 days old – discovered on 26 June (Max Khoo) and predated on 20 July (Low Chong Yang).

Western Singapore

Jurong Lake Gardens, the swathe of park and wetland abutting the Chinese and Japanese Gardens, proved to be a hit for birds. The heronry continued to support various species of large heron, including one Purple Heron, Ardea purpurea, seen on 29 August 2021 by Andrew William. The highly elusive Barred Buttonquail, Turnix suscitator, proved no match for Norhafiani A Majid who spotted one on 30 August 2021, along with a pair of Buffy Fish Owl, Ketupa ketupu. Other birds that provided considerable excitement and cardio workout included the rarely seen Brown-streaked Flycatcher, Muscicapa williamsoni, on 29 August 2021, which was spotted by the keen and young eyes of Kaeden Sim, as well as a migratory Yellow-rumped Flycatcher, Ficedula zanthopygia, female, spotted on 31 August 2021 by Chen Boon Chong.

BW Stilt, 260821, TSA16, Art Toh

Black-winged Stilt seen on 26 August 2021 at Tuas by Art Toh.

The NTU campus yielded a pair of Red-legged Crake, Rallina fasciata, and a Sunda Scops Owl, Otus lempiji, which were spotted on 26 August 2021 by Yip Jen Wei, while a Grey Wagtail, Motacilla cinerea, was seen on 27 August 2021 by Frank Chen. Nearer the Lim Chu Kang cemeteries, a Blue-winged Pitta, Pitta moluccensis, was seen along Jalan Murai on 28 August 2021 by Eyzat Amer.

Visitors to Tuas South Avenue 16 reported seeing a Red-necked Stint, Calidris ruficollis, on 24 August 2021 (Raghav Narayanswamy), Black-winged Stilt, Himantopus himantopus, on 26 August 2021 (Art Toh), Malaysian Plover, Charadrius peronii, on 29 August 2021 (Bear Jia), four Wood Sandpiper, Tringa glareola, on 29 August 2021 (Max Khoo), and a Curlew Sandpiper, Calidris ferruginea, on 30 August 2021 (Pary Sivaraman).

Over at the Clementi Forest-Holland Plain nexus, a Greater Coucal, Centropus sinensis, was reported on 11 August 2021 from Clementi Forest, while four Tanimbar Corella, Cacatua goffiniana, and one Large-billed Crow, Corvus macrorhynchos, were seen around Holland Plain on 30 August 2021. All records were provided by Lynn Tan.

This report is compiled/written by Geoff Lim and Isabelle Lee, and edited by Tan Gim Cheong. We are grateful for the birders and photographers whose postings in various Facebook birding pages, bird forums, individual reports and extracts from eBird make up this report. This compilation is not a complete list of birds recorded for the month and not all the records were verified. 

Many thanks to Lee Chin Pong, Sim Chip Chye and Art Toh for allowing us to use their photographs. 

The Black-Thighed Falconet in Singapore.

THE BLACK-THIGHED FALCONET IN SINGAPORE

Lim Kim Seng

Introduction

The Black-thighed Falconet Microhierax fringillarius was previously classified as a resident breeder as there had been specimens collected from Singapore as well as records since the 1920s and up to the 1990s (Lim 2009) but is likely to have become extirpated thereafter. It was re-categorized by the Nature Society (Singapore) Bird Group Records Committee, or NSSBGRC, as a non-breeding visitor as there have been no confirmed breeding record and no confirmed sightings for thirty years (Lim 2021). The Black-thighed Falconet was put into Category B, a category for wild birds, resident, visitor or vagrant, that have not been recorded for thirty years. In 2021 alone, however, there were three separate records of Black-thighed Falconet and as a result, it was re-instated in Category A by NSSBGRC.

Black-thighed Falconet was re-instated by the NSSBGRC in 2021. Photo taken at Panti Forest by Jimmy Chew.

Global Range, Habitat Requirements, Altitudinal Range, Breeding Habits and Conservation Status of Black-thighed Falconet

The Black-thighed Falconet is a monotypic species first described by Drapiez in 1824. It is one of five falconets in the world, all of which occur in southern China, South and Southeast Asia. Its natural range spans the Thai-Malay Peninsula, Sumatra, Borneo and Java. Its habitat is primary and secondary forests (including on limestone), edges of forests, rubber plantations, fruit orchards, cultivated land, parkland and wooded gardens up to 1,700 m (Ferguson-Lees & Christie 2000, Lim et al 2020, Wells 1999). The Black-thighed Falconet occurs as a common resident in most parts of its range and it is not known to undertake any movements (Robson 2000). In north Borneo, this species is replaced by the endemic White-fronted Falconet M. latifrons (Myers 2009).

In the Thai-Malay Peninsula, it breeds from November to July (Khoo 2021, Wells 1999). Nests are usually in tree cavities abandoned by woodpeckers and larger barbets, mostly in dead trees. In a site monitored in Perak, Malaysia, birds used a cavity in a limestone outcrop and nested successfully (Khoo 2021). Clutch size is three to six. The young remain with their parents for at least two months after fledging (Khoo 2021, Wells 1999).  It breeds from December to June in Borneo (Myers 2009). There is also evidence of communal feeding by birds other than parents, possibly by older siblings, and birds have also been seen to use old nest cavities as communal roost sites (Khoo 2021).

In Perak, Malaysia, they used cavities in Limestone outcrops to nest. Photo: Khoo Siew Yoong.

The Black-thighed Falconet is treated as “least concern” by IUCN (BirdLife International 2016).

Identification and Ecology of Black-thighed Falconet

The Black-thighed Falconet is one of the smallest raptors in the world at 15-17 cm in length from bill tip to tail tip. It is the same size as the White-fronted Falconet but smaller than Collared and Pied Falconets and has the distinction of being the smallest bird of prey of the world! In comparison, the Coppersmith Barbet Megalaima haemacephala measures 15-17 cm, Sunda Pygmy Woodpecker Yungipicus moluccensis, 13 cm and Yellow-vented Bulbul Pycnonotus goiavier measures 19-21 cm. Females are slightly larger than males and an adult weighs about 43 g (Wells 1999). In terms of its jizz, the Black-thighed Falconet has a big-headed, stout-bodied appearance with a medium-sized tail.

The small size of the falconet makes it hard to confuse with other birds although distance may make identification challenging as this species usually hawks from tall trees. It is mostly black on the head, eyestripe, ear patch, upperparts, bill, leg and tail, with mostly white on forehead, eyebrow and underparts, and orange-rufous on throat and lower breast to vent. Juveniles show pinkish horn bill and cere, rusty eyebrow and ear stripe, pale fine edges to upperparts and less rufous on lower underparts.

Its flight is rapid and direct, with fast wingbeats and sharp pointed wings, often accompanied by short periods of gliding.

Its voice is a shrill squeal kweer-week (Wells 1999).

Black-thighed Falconets hunt socially or alone, making sorties from a dead tree. Its diet is mainly arthropods, typically termites, butterflies and moths, dragonflies, carpenter bees, beetles, mantids, grasshoppers and cicadas, birds such as House Swift Apus nipalensis, sunbirds and munias, mammals such as bats and rats, and geckos (Khoo 2021, Wells 1999). Prey is usually snatched on the wing, occasionally from the ground, to be consumed from a perch, and there is evidence that falconets choose flowering trees with an abundance of nectar feeders to hunt (Wells 1999).

Birds indulge in head bobbing and tail wagging in close proximity and allo-preening has been observed (Wells 1999).

Historical Status of the Black-thighed Falconet in Singapore

The earliest reference to the occurrence of the Black-thighed Falconet in Singapore can be found in Bucknill & Chasen (1927) who stated that it “sometimes visit Singapore”. Gibson-Hill (1950) mentioned that it was “resident in small numbers” while RAFOS (1966-1969) and Tweedy (1970) mentioned the existence of several records in the 1960s.

There were no records until almost two decades when I found the first of four sight records within a period of seven years, all from a dead durian tree in my wooded garden in Jalan Ulu Sembawang in the north of Singapore. All records were of singles and included a juvenile seen on the following dates – 11 October 1979, 2 October 1983, 1 December 1983 and 12 April 1986 (Lim 1992). These records indicate the presence of a small and possibly breeding resident population in the area or that of non-breeding visitors from nearby Johor state, Malaysia. There were no further records from this site which was resettled and developed as part of the new Sembawang Estate in the early 1990s. Our most recent record was an adult seen on a dead tree, near the current Ranger’s Station, in the Central Catchment Nature Reserve on 7 October 1990 (Lim 2009).

In addition to these records, there were also four unconfirmed records between 1992 and 2005 from Sime Road, Loyang and Bukit Batok Nature Park. There are also nine specimens collected from MacRitchie Reservoir, Jurong and Singapore in the Lee Kong Chian Nature History Museum collection.  

Due to the fact that there have been no records for thirty years and also no confirmation of breeding, the Black-thighed Falconet’s status was reviewed by NSSBGRC in early 2020 as no longer fitting that of a wild bird for Category A, which is the category for all wild birds recorded within the last thirty years. It was re-categorised as belong to Category B, which is the category for all wild birds recorded within Singapore but not within the last thirty years (Lim 2021).

As fate would have it, soon after the release of the new checklist, news came of our first sighting of Black-thighed Falconet since 1990. This came from a juvenile that was seen and photographed by Lee Lay Na at a HDB block in Yishun Street 71 on 12 February 2021 (Tan, G.C. & Lim, G. 2021). The report of a juvenile is interesting as it indicates local or regional breeding.

A typical perch of the Black-thighed Faconet on top of tree at Goldhill Avenue by Art Toh.

There were two additional records, both also backed by photographs. One was a bird photographed using the top of a tree at Goldhill Avenue on 20 May 2021 by Art Toh (Tan, G.C. 2021) while the second was another adult from Jalan Mashhor on 9 July 2021, reported by Art Toh and Tan Choon Siang, and still present on 12 July 2021, reported by Vincent Lao (Lim, G. et al 2021).

A far away photo of the second adult falconet taken at Jalan Mansor two months later again by Art Toh.

These three sightings from 2021 have the effect of reinstating the Black-thighed Falconet into the Singapore List once again. At the moment, it is probably best considered a rare non-breeding visitor due to the short-term nature of their occurrences in 2021. Hopefully, one day, we will find them nesting in Singapore again.

Concluding Remarks

Birders and bird photographers are much more active than two decades ago. There are people at various locations in Singapore every day and most of them carry some sort of photographic equipment with them. This number of people watching birds daily is bound to yield rewards in the form of documenting the occurrence of rarities as well as species that are either new to Singapore or those thought to have been extirpated. Recent records of Javan Plover and Green Broadbill attest to this increased opportunity of detecting something really sensational!

Would-be falconet seekers are encouraged to focus on sites in the central and north of Singapore, where all confirmed sightings have been made since 1979. Bukit Brown would be another place to pay attention to given the recent record (and nearby, in Goldhill). Searches on Pulau Ubin may also yield results due to the island’s proximity to Malaysia as well as the island’s reputation for attracting Malaysian visitors. Prime habitats to look for this elusive raptor are the edges of forests and woodland as well as areas where there are tall trees or snags.

It is hoped that birders and bird photographers will continue to help us make new discoveries or re-discoveries in the case of the Black-thighed Falconet, the smallest bird of prey in the world.

Acknowledgements

I would like to thank Yong Ding Li for helpful suggestions with the drafting of this article, Jimmy Chew, Khoo Siew Yoong and Art Toh for the use of their photographs.

References

BirdLife International. (2016). Microhierax fringillarius. The IUCN Red List of Threatened Species 2016. Downloaded on 10 September 2021.

Bucknill, J.A.S & Chasen, F.N. (1927).  The birds of Singapore Island. Government Printing Office, Singapore.

Ferguson-Lees & Christie, D.A. (2001). Raptors of the World. Christopher Helm, London.

Gibson-Hill, C.A. (1950). A checklist of the birds of Singapore Island. Bull. Raffles Mus. No. 21: 132-183.

Khoo, S.Y. (2021). Breeding ecology of Black-thighed Falconets in Perak, Malaysia. Nature Society (Singapore) Bird Group. https://singaporebirdgroup.wordpress.com/tag/black-thighed-falconet/

Lim, G., Lee, I. & Tan, G.C. (2021). Singapore Bird Report – July 2021. Nature Society (Singapore) Bird Group.  https://singaporebirdgroup.wordpress.com/category/monthly-bird-reports/

Lim, K.S. (1992). Vanishing birds of Singapore. Nature Society (Singapore), Singapore.

Lim, K.S. (2009). The avifauna of Singapore. Nature Society (Singapore), Singapore.

Lim, K.S. (2021). Bird Records Committee Report (January 2021). Nature Society (Singapore) Bird Group. https://singaporebirdgroup.wordpress.com/2021/02/02/birds-records-committee-report-jan-2021/

Lim, K.S., Yong, D.L. & Lim, K.C. (2020). A field guide to the birds of Malaysia and Singapore. John Beaufoy Publishing, Oxford.

Myers, S. (2009). A field guide to the birds of Borneo. Talisman Publishing, Singapore.

Royal Air Force Ornithological Society (1966-1969). Bulletins of the Singapore Branch & unpublished correspondence with members.

Tan, G.C. (2021). Singapore Raptor Report, Late Spring Migration, April-June 2021. Nature Society (Singapore) Bird Group. https://singaporebirdgroup.wordpress.com/category/raptor-report/singapore-raptor-report/

Tan, G.C. & Lim, G. (2021). Singapore Bird Report – February 2021. Nature Society (Singapore) Bird Group. https://singaporebirdgroup.wordpress.com/category/monthly-bird-reports/

Tweedy, L. (1970). The birds of Singapore. Army Birdwatching Club (Far East).

Wells, D.R. (1999). The birds of the Thai-Malay Peninsula, Volume One: Non-passerines. Academic Press, London.