Thailand’s First “Hartert’s Leaf Warbler”

On January 17th, a photographer found an unusual leaf warbler at Suan Rot Fai (Wachira Benjathat Park), a park located north of central Bangkok. According to him, he only took one picture of it (which I find very unusual) and the bird showed nuthatch-like behaviour. From that single photo, I suspected that it might be the nominate subspecies “goodsoni” of Hartert’s Leaf Warbler (Phylloscopus goodsoni) which has never been recorded in Thailand before. David Gandy, a local birder in Suan Rot Fai area, later relocated the bird on January 31st and took many more photos of it which helped confirm that it is most likely a “goodsoni” Hartert’s Leaf Warbler indeed.

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Hartert’s Leaf Warbler (ssp. goodsoni) is a striking bird with bright yellow supercilium and contrasting crown stripes.

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Another angle showing the highly contrasting crown stripes

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It was mostly silent throughout the observation but briefly gave a few variably high pitched calls. Unfortunately, I wasn’t able to record the calls of it before it went silent again.

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Apart from the supercilium, it has subtle yellow streaks on upper breast as well.

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The undertail coverts are pale yellowish, slightly contrasting to the whiter belly.

I visited the park on Monday morning (2 February 2015) before going to work. Only about 5 minutes after arriving at the location where the bird was found, I could locate the bird foraging through the canopy in a nuthatch-like behaviour. There was also a highly vocal Grey-headed Canary-flycatcher foraging nearby which was a good thing since it helped me locate the leaf warbler easily. It is suspected that the canary-flycatcher follows the leaf warbler to catch the insects which are disturbed by the foraging movements of the leaf warbler.

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My first view of the Hartert’s Leaf Warbler foraging through the main branches resembling Claudia’s Leaf Warbler or a nuthatch.

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Showing underwing and wing formula

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Climbing, looking, hopping

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Showing undertail pattern; note very thin white edge to the inner web of outer tail feathers

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The yellowness of plumage seemed to be very light-dependent. Even with bare eyes, the bird appeared variably yellowish depending on the light.

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David sent some of his photos to seek opinions from Paul Leader, an expert on Asian Phylloscopus warblers, and here’s what he quoted.

“I would agree that this is nominate goodsoni. Within the ‘Blyth’s complex, only nominate goodsoni shows this degree of yellow and yellow streaking on the underparts, such that it resembles a washed out Sulphur-breasted Warbler more than other members of the Blyth’s complex. All of the other members of the complex have clean white underparts with limited yellow streaking (central breast/belly), and this includes Ph. g. fokhiensis.

However, the nuthatch-like behaviour is shared by other members of the complex, at least by claudiae, and therefore is not diagnostic.”

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Showing the subtle yellow streaks on breast

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The striking crown stripes

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Again, the undertail pattern

I followed the bird from around 8.00-8.45 as it foraged through the main branches high up on tree tops and occasionally came down to just about 1.5 m above the ground and disappeared into the canopy again. It was totally an amazing observation and the bird didn’t seem to be particularly skittish, probably because I was the only one there. I guess it would stay around in the same area throughout the winter.

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A confiding Radde’s Warbler

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A female/immature Asian Paradise Flycatcher

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Male White-rumped Shama

Apart from the leaf warbler, there were actually quite a good number of species in the area. There was one Radde’s Warbler which was unusually confiding. I also spotted a female/immature Asian Paradise Flycatcher, Black-naped Monarchs, a very confiding male White-rumped Shama, a pair of nesting Brown-throated Sunbirds, Yellow-browed Warbler, a fly-over Stork-billed Kingfisher and an Asian Barred Owlet. I guess I’ll be visiting this area of the park more often.

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4 thoughts on “Thailand’s First “Hartert’s Leaf Warbler”

  1. Hi Ayuwat,Congratulations for the new species of bird in Thailand. I hope it will be your official contribution.  I think this is not your first new species!  You are an amazing birdwatcher and make very nice reports as well.I go bird watching to the normal places Mae Wong, Kaeng Krachan and the seaside.If you like to go and have not yet been to Phuttamonton Park I would ask you to join me .  We might be lucky and see the Fairy Pitta there, Have a nice dayBen 

  2. Pingback: Suan Rot Fai: 26 April 2015 | ayuwat

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