Air Itam Dalam and Bagan Belat, 22 Mar 2014

Air Itam Dalam has had an exceptional run of hawk-cuckoo records this spring, and Mr and Mrs Hum have been doing a sterling job of documenting them photographically. One of the birds they photographed on 19 March showed several features associated with Northern Hawk-cuckoo, and it was with the aim of studying this bird that I headed to the site early in the morning.

Large Hawk-cuckoo_AID_220314_IMG_1769Unfortunately, the only hawk-cuckoo I could find was this subadult Large Hawk-cuckoo. It was extremely skittish, and disappeared into the thick stuff at the slightest disturbance.

Buffy Fish-owl_AID_220314_IMG_1773 Spotted Wood-owl_AID_220314_IMG_1791 Mangrove Blue Flycatcher_AID_220314_IMG_1775 Forest Wagtail_AID_220314_IMG_1790Some of Air Itam Dalam’s ‘regulars’ – roosting Buffy Fish-owl and Spotted Wood-owl, Mangrove Blue Flycatcher and Forest Wagtail.phyllosc_AID_220314_IMG_6417

There was also a ‘Pale-legged type’ Leaf Warbler, which showed well at times. Recent records in the Gulf of Thailand and Singapore suggest that Sakhalin Leaf Warbler may be the commoner of this difficult species pair in the Peninsula, so I was eager to see how it would respond to playback of the songs of both species. The result? It showed no visible response to either! Big disappointment!

Tim and I were hosting a visitor from England who was keen to see some shorebirds, so we headed for the coast at Bagan Belat, where the tide was low and the shorebirds were predictably distant.

However, I was surprised to hear the familiar tink call of another ‘Pale-legged’ Leaf Warbler coming from the coastal scrub, so in I went again with my playback of the songs. First I played the song of Pale-legged for about 3 minutes. No sign of the bird. Then I played the song of Sakhalin Leaf Warbler. The response was almost immediate!

Sakhalin Leaf Warbler_Bagan Belat_220314_IMG_6429Overhead and looking down for the intruder.

Sakhalin Leaf Warbler_Bagan Belat_220314_IMG_6508Over the next hour or so I played the songs of both species again, and each time I played the Sakhalin Leaf Warbler song, I got the same immediate response.

Sakhalin Leaf Warbler_Bagan Belat_220314_IMG_6565I did not manage to hear or record the song, but this photo shows that it was clearly singing!

Sakhalin Leaf Warbler_Bagan Belat_220314_IMG_6648There’s no certain way to differentiate these in the field other than by song. Even in the hand, there is apparently quite an overlap in wing length, with only  birds at either end of the spectrum (Sakhalin has longer wings, Pale-legged shorter) being identifiable with certainty.

Several observers have noted that Sakhalin’s tink call is lower-pitched than Pale-legged, and if you compare the calls of birds identified by song, such as this Pale-legged and this Sakhalin (in Singapore!), and their accompanying sonograms, the difference in pitch is quite evident, with Sakhalin being around 5kHz and Pale-legged around 6kHz. In addition, to my ears, Pale-legged sounds thin and weak, whereas Sakhalin’s call is appreciably fuller. I was not able to record the call of the Bagan Belat bird, but all my recordings of birds in Perlis are lower-pitched, some even lower than the Singapore bird. The only fly in the ointment of this potential differentiating character are two recordings of apparently the same bird (though it was not actually seen) giving both call types, made in Hangzhou Bay, China by Frank Lambert. This recording is of a thin high-pitched call (around 6kHz), while this one sounds identical to that of the Singapore bird to my ears (and is around 5kHz). This anomalous example apart, a survey of calls of Pale-legged Leaf Warbler on xenocanto in Vietnam and Cambodia reveals that all of the recordings are of the thin, higher-pitched call associated with Pale-legged. Another bird recorded in Hangzhou Bay sounds much more like Sakhalin, a possibility noted by Frank in the notes accompanying the recording.

So, are there any certain records of Pale-legged Leaf Warbler in Malaysia? Wells (2007) gives the range of wing lengths of 7 skins from the Thai-Malay Peninsula as 59-68mm. Birds at the lower end of this range should be Pale-legged, but, for the time being at least, Pale-legged should probably be square-bracketed as a Malaysian bird.

In the meantime, anyone heading to Perlis in the next few weeks would be well-advised to carry a recording of the song of both species (downloadable from xeno-canto), and a recording device to document any response.

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7 thoughts on “Air Itam Dalam and Bagan Belat, 22 Mar 2014

  1. Oh God – another split. Leaf Warblers are difficult just as they are and call is the only difference you say. Nice shots, by the way.

    • Mun, the song is the real difference – completely different from each other. The calls are rather more similar, and need to be recorded and then compared to recordings of birds of known identity I would suggest.

  2. The Pale-legged Warbler above looks very convincing. It is at least regular in the Penang National Park, and was very late last year, an individual was present until at least mid-May with a whole bunch of ficedula flycatchers.. Pale-legged has a totally different behaviour and possibly even a different wintering, micro-habitat preference. A ‘ fuscus’ Reed Warbler like rump together with plain undertail coverts, not the well saturated, yet still very ephemeral, yellow ones obvious in some races of the other species is very indicative of Pale-legged. The olive-slate head of Pale-legged seems evident as well in the above photograph. The “Sakhalin’ photos look a bit like Pale legged as well but presumably these birds frequented the mid to upper canopy like borealis? Pale-legged is perhaps the most bulky of all the so called leaf warblers.

  3. Dave, the Ayer Itam Dalam bird is showing now and responds to playbacks of only the Pale-Legged! It also keeps to the mid-storey rather than close to the ground. Another birder named James Neoh (not my relative!) has decent pics of this species which I will forward to you. He is also trying his best to record the call of the actual bird itself, although the bird has largely been silent during observations.

  4. I was very pleased after writing the above to get fairly clear recordings (for a smart phone) of the many singing males in Penang National Park. I wrote a comment on xeno canto about these recordings which I hope to download at some point in time. I have an open mind but can only say that Pale-legged is regular in mid-May in the PNP.

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