Tickell’s Leaf Warbler

In the evening of 1 January 2021, I decided to visit Mae Faek paddies with the aim to get some nice photos of common farmland birds. It was a very pleasant evening with nice cool winter breeze and really nice lighting. The condition was perfect for photography. While I was enjoying some nice views of the local Plain-backed Sparrows, I noticed a small warbler foraging in a mimosa tree in the background. I snapped a few shots of the warbler and checked the photos to see what it was. To my surprise, it was a Tickell’s/Alpine Leaf Warbler, a very rare bird in Thailand! I ended up spending that evening following it around until sunset. It certainly became one of the most memorable New Year’s days I’ve ever had.

One of the photos that I took on the very first day that I found it (1 January 2021)
It mostly foraged among the mimosa trees looking for all kinds of small insects (9 January 2021).
The preys that it caught included spiders, damselflies, aphids, ants and various types of flies.
There were so many insects emerging from the mimosa trees in the evening. I’m not sure what they were, but they looked like flying ants to me. (6 January 2021)
Once the insects began to emerge, it became really easy to approach and photograph the bird while it was busy catching the insects (6 January 2021).
I visited the site almost daily and got many photos of the bird at close range, particularly while it was foraging on the emerging insects in the evening (4 January 2021).

After my first encounter, I visited the site almost daily to observe it. The bird proved to be very territorial. It spent most of the time foraging in a small area of mimosa trees surrounded by a paved road. It sometimes flew over a short brick wall to feed in a larger area of mimosa trees on the southern side, but usually returned to its main territory within less than an hour. It was quite clear that the main reason for it to stay in such a small territory was the abundance of food. There seemed to be some sort of insects that emerged from the mimosa trees daily in the evening around 5 PM onward. To me, they looked like flying ants but I really can’t be sure. Once these insects came out, the bird became very easy to approach and photograph.

The area didn’t look particularly good for birding, but surprisingly it was. The bird spent most of its time foraging among the short mimosa trees in the middle between the two roads.
It was the most conspicuous warbler in that area, moving slowly from one exposed perch to another. Other warblers in the same area, including Dusky, Yellow-browed and Lanceolated Warblers, were all shyer and more skittish.
It often descended to feed close to the ground, particularly when joining the mixed-species flock consisted of Plain Prinias and Dusky Warblers.
It was moulting some of its tail feathers. The new feathers were brighter olive with darker centres (7 January 2021).
It took nearly a month for the new feathers to grow completely (20 January 2021).
Plumage colour appeared to be easily affected by the light. In cloudy and overcast weather, the plumage appears bright lime-yellow (9 January 2021).
Whereas during sunny midday, it appeared duller because of the shadowing on the underparts (4 January 2021).
In the warm early morning and late evening light, it usually appeared more buffish and could resemble the similar Buff-throated Warbler.

The bird was last seen on 20 February 2021 by Chintana Suwawan, a Chiang Mai birder. Even though it stayed around for nearly 2 months, its identity was never completely solved as the identification of Tickell’s/Alpine Leaf Warbler away from the breeding ground is not well understood. I got some recordings of the sub-song that it made. The sonogram looked a bit more like Alpine Leaf Warbler, but it was hard to be sure. Fortunately, a paper on bioacoustic, morphological and phylogenetic data which came out in 2019 has suggested a lump between Tickell’s and Alpine Leaf Warbler, and the lump was finally accepted in the latest IOC Checklist in 2021. I’m pretty sure that other checklists will soon follow and only Tickell’s Leaf Warbler (Phylloscopus affinis) will remain as a species.

Buff-throated Warbler (P. subaffinis) has a very similar plumage but can only be found on high mountains. Note the more buffish overall colouration (instead of lime-yellow) and more black on the lower mandible (Doi Lang (west), 1 January 2020).
Tickell’s Leaf Warbler has a different shade of yellow with much less black on the lower mandible (11 January 2021).

This bird that I found at Mae Faek is the third confirmed record of this species in Thailand. The first record was a bird from Hang Dong, Chiang Mai found by Thammarat Kaosombat on 17 January 2020, then followed by a bird at Mae Rim, Chiang Mai on 9 December 2020 by Nitaya Jotikasthira. After I found the Mae Faek bird, another bird was also seen and photographed by Jens Toettrup at Pong Daeng, Tak on 31 January 2021, making the total of 4 records of Tickell’s Leaf Warbler in Thailand so far. All 4 records were from similarly open area with sparse shrubs and trees in lowland. I think habitat and elevation can certainly be used when identifying Tickell’s and Buff-throated Warbler, as the latter is only found in open forest on high mountains. Apart from that, Buff-throated Warbler also has a more buffish overall plumage (instead of lime-yellow) with more black on the lower mandible. I’m already looking forward to seeing more records of the Tickell’s Leaf Warbler in the upcoming winter, as it seems to be a regular but criminally overlooked species here in Thailand.

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