Saturday, May 12, 2018

Some Simple Analysis of the Call of the Booted Warbler

Some Simple Analysis of the Call of the Booted Warbler

A warbler visited Kranji Marsh in Dec 2017, and was first noted by Martin Kennewell.  It looked like a booted or sykes's warbler.  The two are similar-looking and have their wintering range in India.  Experts decided it was booted.  Some simple analysis of the call supports the finding of booted.  The whole vocalisation is a jumbled chortling and squealing characteristic of warblers, and includes a repeated hard churr, and a repeated, short shtick call.  

1.  The churr call is made by booted but not by sykes's warbler. 
I recorded a churr call of 0.3 to 0.4s duration, the warbler responding to a nearby oriental reed-warbler.   Interestingly it responded to another warbler of a different genus but within the same Acrocephalidae family.  Video recording was made on Olympus EM-1 camera, audio file was extracted for analysis on Raven Lite 2.0.



Fig. 1  Spectrogram of the warbler call, zoomed-in on the response to the oriental reed warbler

This is known behavior of the booted warbler.  Rasmussen and Anderson, in Birds of South Asia mention this churr call.  There are two records of this churr call on xeno-canto, both from India.  The churr call is not recorded in it's breeding range.  Both records have a similar call duration of 0.3 to 0.4s.  Frequency ranges of the calls are roughly similar but it is difficult to be certain because of the noise in my recording.

Duration (s)
Pitch (kHz)
Sg warbler
2 to 6 or 7.5 (the upper bound cannot be seen clearly because of noise)
Booted warbler

1 to 6 or 7.5
1.3 to 7.9

So the churr call is similar to previous recordings of this call for booted warbler.  While there are no recordings of such a call by sykes's warbler on xeno-canto.

2.  The short shtick call is more similar in duration to that of booted warbler.

Comparison was made between 2 xeno-canto recordings  made by Yong Ding Li and Lim Kim Chuah in Jan 2018 which feature this shtick call, and some reasonably clear recordings of booted and sykes's warbler from India.  There are not that many on xeno-canto. 

At an average 0.031s duration, the shtick call on the Sg warbler is more similar to the booted warbler.  

Duration (s)
Sg Warbler

YDL, XC400778
LKC, XC400748
Booted Warbler

Sykes’s Warbler


Fig 2. Spectrogram of Sg Booted Warbler Call, recorded by Yong Ding Li

Friday, July 28, 2017

Way Kambas 18 to 21 July 2017

Gould's Frogmouth.
Picture Gallery on Smugmug:  


 As elsewhere in Indonesia, very little undisturbed forest remains in Sumatra.  Way Kambas, 1,300km2 preserves some remaining lowland rainforest. It was established as a game reserve by the Dutch in 1937, then after independence, it went for a period without protection until declared a national park in 1989.  It has been logged and the valuable timber trees stripped, but has regenerated somewhat, and still provides good habitat. Credit to two 2016 books for lighting up the birding trails of Indonesia; ‘100 Best Birdwatching Sites in SEA’, by Yong Ding Li and Albert Low, where Way Kambas finds mention, and the long-awaited field guide ‘Birds of the Indonesian Archipelago’, by James Eaton.

What would draw an Sg birder here?
·   Nightbirds.  The rare, endemic bonaparte’s nightjar, and the large, gould’s and sunda frogmouths are quite reliably seen.  In addition, there is a small population of the endangered white-winged duck .  The other birds are mostly in common with Pen Mal as WK is in the Sundaic region.  So that means 5 mega birds.

·   Easy birding.  Birding is along an unpaved jeep trail on flat ground. The Satwa Ecolodge is just outside the park entrance, with basic but clean and spacious rooms.  Crucially, there is a good local guide, Hari attached to the lodge.  Finally it is just 2 hrs drive from Bandar Lampung airport, compared with the 6-hr drive from Padang to Kerinci-Seblat National Park.  You can be birding within 8 hrs of take off from Changi. 

One would not come to WK for the Sumatran endemics though.  There are 26 or so, depending on the authority.  But 21 are in the highlands.  As in all the tropics, there is a distinct montane avifauna, with a higher degree of endemism. Another 4 are on the Barusan Islands off the Indian Ocean coast, separated by a deep sea trench.  This leaves only the sumatran babbler to be found in WK.  If pursuing endemics the prime destination is Kerinci-Seblat, but that is another trip

National Parks of Sumatra

Some interesting mammals have a toehold in these forests.  The siamang gibbon is easily seen, feeding in canopy.  Other primates are spectacled leaf monkey and pig-tailed macaque.  Sambar feed at the Rawa Gajah marshes.  The Elephant Conservation Center is open for visits.  There are a handful of sumatran rhinos in the wild here and 7 in the Sumatran Rhino Sanctuary, not open for visits.  20 tigers are known from the camera traps.  But Hari has not seen them in his 10 yrs here and they will not be encountered.  Numbers of big animals are slowly declining unfortunately.  


Birding is done along the unpaved jeep trail, stretching 13km from entrance gate to the Way Kanan ranger station, on the banks of the Sungai Way Kambas.  Along this trail, woodpeckers, malkohas, bulbuls and babblers abound.  At Way Kanan is a big clearing by the river but we did not bird much there.

Sketch map of Way Kambas

Good birding was also had along the road to the Elephant Centre, which heads south from the entrance gate, following the edge of the park.  This road yielded large and sunda frogmouths, brown wood owl and brown hawk owl.  For the white winged duck, we took a boat up the Sungai Way Kambas for a bit, then walked 10 mins to the Rawa Gajah (Elephant Swamp) marsh and waited.  A pair of ducks flew in at 5pm.  They are wary so we stayed 200m away, beyond photo range. Hari says I have been lucky to get all 5 mega birds over 3 nights.  Credit to his fieldcraft.

Main Trail from Entrance to Way Kanan.  Mandatory machete-armed rearguard ranger to protect from tigers.

The freshwater marsh at Rawa Gajah, where the white-winged ducks can be found.

Summary of birds seen, by family.
A profusion of malkohas; raffles, chestnut bellied, green billed, red billed.
Hit jackpot here, with large, gould’s and sunda.  With much thanks to Hari.  Only the gould’s was on daytime roost.  To find the roost, he notes where they call at night, and searches the spot by day. 
Bonaparte’s, malaysian eared and large tailed.
Oriental bay, brown wood and brown hawk.
Orange-backed, buff-necked, grey-and-buff woodpeckers, rufous piculet
Rufous collared, oriental dwarf, banded.
Dusky broadbill.
Malayan banded pitta seen quite regularly. 
Black-capped, scaly-crowned, sooty-headed, sumatran, ferruginous, chestnut-rumped, fluffy-backed tit, black-throated, sunda scimitar.  The Sundaic babblers are well represented.

Notable birds not seen were storm stork, lesser adjutant, great argus.  An argus lek was once discovered but once a hide was set up, they ceased lekking.   

WK is not a place for studio photographs of birds.  No hides, as there are tigers.  As elsewhere in Indonesia, the birds have grown wary from relentless trapping and do not allow close approach.  WK is a little better in this regard. The main trail which is narrow, with a narrow break overhead in the continuous canopy and little sun coming through, unlike the Panti ‘bunker trail’.  Most of my shots were at maximum ISO cap of 1600.  Babblers present at mid-canopy to ground level, resulting in shutter speed 1/15s handheld.  Kingfishers similarly.  Torch-lit night birds at 1/8s.  Getting to the calling night bird, circling for a decent view and sometimes following its movements, involves some off-trail jungle-bashing.


Hari excelled, with an uncanny ability to hear the direction of the night bird and put his torch on it.  Understands photogs, will find a good angle, will locate the flitting bird again and again.  Has been guiding at WK for 7 years, referenced in many trip reports.  But his bookings are pretty busy, We birded by jeep, walking at promising stretches.  Occasionally had to jungle-bash, but there were few thorny plants, or trippy lianas.  Entry to the reserve was at our choice of timing, most mornings at 5am for a spell of night birding before the dawn at 6am. Service was good.  One night we were birding Way Kanan, when an oriental bay owl called from across the river, one of my target birds.  Hari roused up the rangers to launch the boat for the crossing and we bagged it.  In general, birding hours were 5am to 11am, with a break for lunch and a tidor, then again from 3pm to 9pm, with packed dinner.

Getting There

Outbound, Sg-Jakarta, with Garuda, 7.25-8.15am.  Then Jakarta-Bandar Lampung, with Sriwijaya, 11.15-12pm.  This gives 3 hrs to transfer terminals in Jakarta. (In the event, when I got to Jakarta, the Lampung flight was delayed 4 hrs.)   Transferring terminals is a hassle.  There is a free shuttle bus every 10 mins, but it’s not a low-floor and luggage has to be carried up 3 steps.  The bus also gets crowded.  Lampung is a small, modern airport so in and outbound was fast and easy. Lampung to Way Kambas is a 2 hr drive on a good road.   


Satwa Ecolodge, no aircon, no hot water, but clean and spacious and set in a nice garden. Don’t expect much birding in the garden though. Lodge restaurant food was simple but tasty.
Soto ayam prepared by the 3 ibus, a typical meal at Satwa

It’s also possible to stay at the very basic lodge at the Way Kanan ranger station.  But bring and cook your own food. 

When to go

May to Sep to avoid the rainy season.  Ref the climate chart for Jakarta, 200km south east.  The most popular month is July from trip reports. 

Climate chart for nearby Jakarta


‘Birds of the Indonesian Archipelago’, 2016, by James Eaton

‘100 Best Birdwatching Sites in SEA’, 2016, by Yong Ding Li and Albert Low

Birdtourasia, 2016 report

Trip report by Oscar Campbell, 2012

Birdquest trip, Janos Olah, 2012,

Bird list for Way Kambas. Could not find one, so I used the Avibase list for Lampung province, and cross-referenced the field guide to knock out all the montane species which would only be found in Bukit Barisan Selatan National Park. This resulted in a workable list which could be checked with Hari.