The Acrocephalus Issue

When talking about Little Brown Jobs or those small birds that are difficult to identify, most birders in Thailand would immediately think of the Phylloscopus warblers because there are so many species of them. They’re definitely one of the birders’ ultimate nightmares. But for me, I’d say there are something even more frightening than identify the Phyllocs, the Acrocephalus warblers!

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Oriental Reed Warbler is the commonest and most widespread Acros in Thailand.

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Mostly seen foraging along scrubs and grassy area near water.

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Frequents perching in the open to dry itself up in the morning. Note pale tip to tail feathers.

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Can be rather showy and perch on grass top for a look out or to sing before spring migration

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Note long and pointy primary projection

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Often shows hint of greyish streaking on breast (more prominent in spring)

There are 8 species of Acrocephalus warblers, or generally called “reed warblers”, in Thailand. They can be divided into 2 main groups, the large and the small reed warblers. Only 2 species are considered as large reed warblers; the Oriental Reed Warbler and the Clamorous Reed Warbler. These two are approximately 20 cm in length or about the size of a bulbul. The latter is an extremely rare vagrant OR a highly overlooked species in Thailand with very few accepted records, while the former is the commonest and most widespread reed warbler in the country. The identification of these two species is extremely challenging (definitely more challenging than what it seems in the guide books!). I still haven’t been able to scrutinize all the large reed warblers that I’ve seen, so I assume that all of them are Oriental Reed Warbler for the meantime.

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Among the small reed warblers, the Black-browed Reed Warbler is the commonest species.

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It’s about the same size and at times can resemble a Phylloscopus warbler like Dusky Warbler or Radde’s Warbler.

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Most of the time, the black eyebrow is thick and obvious enough to separate it from other similar species.

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But other times, the black eyebrow can appear faint and thin.

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But that might depend on the angle!

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Or the angle plus lighting

What about the other 6 species of reed warblers in Thailand? They’re all small-sized reed warblers which are approximately about the same size as a sparrow, or just a little larger than most Phyllocs. The commonest and most widespread species among these small reed warblers is the Black-browed Reed Warbler.

With a prominent black eyebrow over the pale supercilium, you might think that it’s quite straightforward to identify this species. Most of the time, it is indeed, but every once in a while, you’ll come across odd individuals that look like it might be a different species.

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Manchurian Reed Warbler is listed as Vulnerable by the IUCN Red List. I photographed this bird in my local patch in Mae Taeng, Chiang Mai on 18 September 2004. It is still by far the only record of this species in the north.

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Note completely pale tip to lower mandible (mostly blackish in Black-browed RW). For Manchurian RW, this can turn blackish only in spring and summer.

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Structurally, it is more similar to Paddyfield Warbler (which was once treated as the same species) than Black-browed RW. The tone of plumage is also warmer and more rufous-tinged like Paddyfield Warbler rather than Black-browed RW as well.

The species that is most often confused with Black-browed RW is the globally threatened Manchurian Reed Warbler. It is a  range-restricted breeder in China that winters in South-East Asia. In Thailand, it is reported to be a passage migrant in the north and central part of the country and spend winter along the eastern coast of southern Thailand. Recently, it was also found to be wintering in Malaysia and Cambodia too.

When compared to Black-browed RW, the Manchurian RW generally shows a different structure by having longer tail and longer bill. The lower mandible also lacks dark tip unlike in Black-browed RW which shows dark tip to lower mandible throughout winter. In Manchurian RW, the dark tip is only developed in spring and summer. The plumage is also warmer and more rufous-tinged similar to Paddyfield Warbler, which it was once treated as the same species. The black eyebrow is often faint and thin and the pale supercilium tend to be thinner and more pointy at rear end than in Black-browed RW.

Note: be aware that some Black-browed RW can also show faint/thin black eyebrow too! Better photos and more identification notes on Manchurian/Black-browed RW can be read from Dave Bakewell’s post here.

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Paddyfield Warbler is a rare winter visitor to small areas of northern Thailand.

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This adult bird was ringed at Nam Kham Nature Reserve in February 2014 and was found to be a regular visitor at the Rubythroat Hide in 2016.

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Bill is rather short and shows prominent dark tip to lower mandible throughout winter.

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Plumage is warm rufescent-brown with rather short primary projection

Things get even more confusing with the small reed warblers that lack black eyebrow. Let’s start with the Paddyfield Warbler, a bird that is quite widespread in Europe and Asia but is a rare winter visitor in Thailand. The Manchurian Reed Warbler was once treated as a subspecies of Paddyfield Warbler and it’s no surprise. They share many similar characteristics like warm rufescent-brown plumage and very similar wing formula and length of primary projection. The Paddyfield Warbler can often show a hint of dark eyebrow over the pale supercilium as well, but never as black as in Manchurian/Black-browed RW. However, unlike in Manchurian RW, the Paddyfield Warbler always shows dark tip to lower mandible throughout the winter. The bill is also shorter and more pointy at tip than in Manchurian RW. In Thailand, it can only be found in several locations in northern part of the country including Nam Kham Nature Reserve in Chiang Rai where these photos were taken.

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Blunt-winged Warbler is one of the trickiest birds to see and even trickier to identify!

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It’s one the small reed warblers that lack any trace of dark eyebrow, which makes it look rather plain-faced.

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I probably wouldn’t be able to identify this bird without this lucky, even though blurry shot that shows the wing formula.

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Note the long P1 that extends beyond primary coverts

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Structurally, it’s a small Acros with long tail.

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Supercilium is short and not as prominent as in Paddyfield Warbler.

But the most challenging group of all reed warblers, or probably all LBJs, is the plain-faced small Acros! There are 3 species recorded in Thailand; the Blunt-winged Warbler, Blyth’s Reed Warbler and Large-billed Reed Warbler. All three species share some very similar characteristics including the lack of dark eyebrow, long bill and shortish supercilium which is not so prominent making them look rather plain-faced.

The commonest and most widespread species among the 3 is the Blunt-winged Warbler which is a winter visitor to wetlands throughout northern and central Thailand. Despite its abundance, it’s never easy to see one because it’s a very shy and skittish bird. Even though you finally get to see it, the bigger challenge would be to identify it!

It’s almost impossible to identify these small plain-faced reed warblers without seeing the wing formula.

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Left: Blyth’s Reed Warbler; Right: Blunt-winged Warbler

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Left: Blunt-winged Warbler; Right: Blyth’s Reed Warbler. Note the short and blunt primary projection as suggested by the name in Blunt-winged Warbler.

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The long P1 which extends beyond the primary coverts is another main ID feature for Blunt-winged Warbler.

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Blyth’s Reed Warbler is a rare winter visitor in Thailand. Note the much shorter P1 and shorter tail than in Blunt-winged Warbler.

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Primary projection is much longer and more pointed than in Blunt-winged Warbler.

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Blyth’s Reed Wabler (left) tends to have colder brown and often grey-tinged plumage than in Blunt-winged Warbler (right). The supercilium is also more obscured in Blyth’s RW.

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Blunt-winged Warbler in profile; note rather warm brownish plumage and short but distinct supercilium.

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Blyth’s Reed Warbler in profile; note cold greyish-brown plumage and less prominent supercilium

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When seen in the field, the Blyth’s Reed Warbler is generally a long-billed and short-tailed bird.

The Blyth’s Reed Warbler is a rare winter visitor that has only been recorded several times from 2 locations in Thailand; i.e. Nam Kham Nature Reserve in Chiang Rai and Bung Boraphet in Nakhon Sawan. Compared to the Blunt-winged Warbler, it has colder and overall more greyish-brown tone to the plumage with much longer primary projection and shorter tail. Its P1 is also shorter and doesn’t markedly extend beyond primary coverts like in Blunt-winged Warbler. Behaviour-wise, the Blyth’s RW prefers dryer areas with scrubs or forest edge near wetlands, while Blunt-winged Warbler is a strictly wetland bird that can only be found in reed beds.

Finally, the most challenging identification among all reed warblers (and LBJs, in my opinion) is between the Blyth’s and Large-billed RW. The Large-billed Reed Warbler is an extremely rare and very little known species which has only been recently rediscovered in 2006 by Philip Round at Laem Phak Bia in Phetchaburi and followed by another record from Nam Kham Nature Reserve in 2008. Basically, the Large-billed RW has longer bill and warmer tone to the plumage, but these two can overlap in almost every morphological aspect. There was even one bird at Nam Kham Nature Reserve that we weren’t able to identify even after measuring it in hand, so DNA test was required! In the end, the DNA result revealed that it was a Blyth’s Reed Warbler. I’m not going to touch on how to identify these two, so here’s a photo of a true Large-billed Reed Warbler from Nam Kham Nature Reserve instead.

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The second record of Large-billed Reed Warbler in Thailand from Nam Kham Nature Reserve. Photo by Woraphot Bunkhwamdi.

Warbler’s Time

Late March is definitely the best time for Little Brown Jobs in Thailand! Before taking on their long-distant journey back to the breeding grounds, these elusive brown little birds would start practising their remarkable songs which are rarely heard in this part of the world. During my last visit to Chiang Rai, I stayed at the beautiful Chiang Saen Lake where I photographed many photos of the elusive Pallas’s Grasshopper Warbler and Black-browed Reed Warbler last year. Both species were showing exceedingly well once again. I’m sure that Chiang Saen Lake is the best place in Thailand to see them!

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Singing Pallas’s Grasshopper Warbler

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I noticed this Pallas’s Grasshopper Warbler singing in thick vegetation very early in the morning. After a few playbacks, it came up really close to where I was sitting and started to sing its melodic song right in front of me. The song sounds more similar to an Acrocephalus reed warbler’s song rather than a Locustella warbler’s since all other Locustella warblers in Thailand have weird monotonic insect-like songs.

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Black-browed Reed Warbler with Water Parsley

After the grasshopper warbler was gone, I continued my effort to photograph the more numerous Black-browed Reed Warblers. Despite being way more abundant, they didn’t respond to playbacks as much as the grasshopper warbler. Photographing them wasn’t as easy as it seems, but in the end, I could get some satisfying shots with the beautiful Water Parsley (Oenanthe javanica) which were blooming all over the marsh.

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This individual seems to be partially leucistic.

But there’s a specific area where these Black-browed Reed Warblers seemed to favour. It was a small corner with medium sized sedge right next to the house where I was staying. At least 3 Black-browed Reed Warblers showed up there at once, as well as a Pallas’s Grasshopper Warbler which came up to preen and sunbath.

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Too bad, the above shot which shows the full body of the Pallas’s Grasshopper Warbler is so blurry because the speed was low and the bird was walking up the stalk really fast. Otherwise, I would’ve got my best photo of this species that I like.

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This individual has already completed its moult making it look very neat.

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What a cute looking reed warbler!

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Another set of a curious Black-browed Reed Warbler to end this post. It’s always fun for me trying to get photos of these birds that are mostly overlooked because of their drab plumage and shy behaviour. I’m now already planning for a reed warbler photography trip next spring. This time, I’ll be focusing on the scarcer ones like Blunt-winged, Blyth’s, Paddyfield and hopefully Large-billed Reed Warbler at Nam Kham Nature Reserve.

Chiang Saen: 6 March 2014

On the next morning, we visited Nam Kham Nature Reserve once again but a little earlier than the first visit because I wanted to photograph the Brown-cheeked Rails before the light gets too strong. The bird was already there when I entered the hide and the mission was accomplished without much effort.

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According to Tavares, Kroon & Baker (2010), the race ‘indicus’ which was formerly considered as a subspecies of Water Rail (Rallus aquaticus) has been split into a monotypic species Rallus indicus, commonly called either Brown-cheeked Rail or Eastern Water Rail according to the characteristics of having brown cheek patch and distribution range from East Siberia to South-East Asia.

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I was done with the rails just within about half an hour. Other birds seen from the hide on that morning included a male Common Kingfisher which posed as a nice foreground for the rail. A Black-browed Reed Warbler, the same Pallas’s Grasshopper Warbler and the same Siberian Rubythroat also showed up briefly as well as a flock of about 10 Greater Painted-Snipes of which 2 of them were females.

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As we were leaving from Chiang Saen Lake, we spotted this female Spot-breasted Woodpecker with a mouthful of food. The nest must be somewhere nearby but we didn’t have the time to follow up.

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Where else can you see a Pallas’s Grasshopper Warbler together with a Brown-cheeked Rail!?

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The rail just couldn’t stop photobombing other birds.

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A moulting Black-browed Reed Warbler which showed up briefly.

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The only Common Snipe at the pond

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The same Green Sandpiper was still showing well. Some new breeding feathers were already visible.

I got out of the hide and decided to take a walk in the reed bed. While walking towards the main shelter in the middle of the reserve, I heard a familiar song which was very similar to the song which I used to hear very often when I was in Japan. I knew right then what it was, the rare Manchurian Bush Warbler. Even though the song was not exactly the same as the Japanese Bush Warbler, it sounded very similar. I followed the song and could finally catch a glimpse of the male bird singing through the bush. It was surprisingly large, much larger than the Japanese Bush Warbler.

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I didn’t have the time to grab any photo, so here’s a sketch of the scene when I saw the Manchurian Bush Warbler.

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I also came across a singing small Acrocephalus reed warbler in tall reed. Even with a couple of recordings of the song and a very brief glimpse of the bird, it still can’t be firmly identified. The closest guess is Blunt-winged Warbler.

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The same male Common Kingfisher in better light

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Despite being very common, it’s hard overlook such beauty.

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A different male Siberian Rubythroat from yesterday. It was ringed and feeding along the water edge.

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The ‘ruby’ throat really stands out among the mud.

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I spent the last hour at Nam Kham in a different hide on the other edge of the pond. There was a different male Siberian Rubythroat constantly showing up around the water edge. Another Pallas’s Grasshopper Warbler was also seen but was too fast for a photo. Around 11am, I left the area and had a nice lunch by the Mekong River in Chiang Saen then take a ride back to Chiang Mai.

Chiang Saen: 5 March 2014

I drove up to Chiang Saen on the afternoon of March 4 along with Dr. Chaiyan Kasorndokbua who went to conduct a research on harriers. We arrived at the Chiang Saen Lake late in the evening and didn’t have much time to do a lot of birding. At least, I managed to lure out a Pallas’s Grasshopper Warbler and a pair of Black-browed Reed Warbler, exactly at the same area where I found them last year.

We stayed at the lake and on the next morning we were greeted with lots of birds around the lake. Grey-headed Swamphen, Common Moorhen, White-breasted Waterhen, Little Grebe and Lesser Whistling Ducks were very common. A young Racket-tailed Treepie even showed up right in front of our house.

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Early morning at Chiang Saen Lake

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The first Brown-cheeked Rail that we found

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One of the many Baikal Bush Warblers

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A worn Greenish Warbler with new set of greater coverts. Even thought the wing bar seems unusually large but overall colouration suggests Greenish over Two-barred Warbler. It has already been ringed!

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We quickly moved to Nam Kham Nature Reserve to look for the scarce Brown-cheeked Rails, a former subspecies of the Eurasian species Water Rail, which were reported about a week earlier. I found the bird as soon as I entered one of the hides on the edge of the big pond. The bird was feeding alongside a Ruddy-breasted Crake, but it was extremely difficult to photograph since they were feeding in a dense area.

I later decided to walk around in the reed bed hoping to find some little brown jobs. I came across quite many Baikal Bush Warblers but could only grab a record shot of one bird. A Black-browed Reed Warbler and a worn Greenish Warbler were also found.

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Brown-cheeked Rail feeding on aquatic insect

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Finishing the meal

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Note the brown cheek patch, a characteristic different from the European Water Rail

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It liked to swim and look for food. Here it caught a big fish.

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One of the 2 male Siberian Rubythroats which were feeding around the edge of the pond. This one had a large insect for breakfast.

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I later met a small group of foreign birders who told me that a pair of Brown-cheeked Rails were showing very well at a different hide on the other side of the pond. I spotted a bird feeding on the edge of the pond as soon as I arrived at the hide. It was busy feeding on various types of food including fish, snails and some aquatic insects that I have no idea what they are.

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In total, I estimated about 5 different Brown-cheeked Rails. Here’s a different one which came closest to the hide.

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Note also black markings on white undertail coverts different from the plain white undertail covert of European Water Rail

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Here’s a compilation of video clips that I took. Later in the video shows 2 birds chasing each other.

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Shame about the strong light coming from the side which darkened most of the details and over exposed some parts of the bird.

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This Pallas’s Grasshopper Warbler was also feeding along the water edge. It had a deformed lower mandible.

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Showing the ‘rusty rump’ and black streaks on the back

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There was only 1 non-breeding Green Sandpiper. Normally, this species is quite common in this area.

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I spent about an hour at a different hide in the reeds hoping to see some birds that came to bathe but there was only this Dusky Warbler which showed up.

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In the evening, I decided to spend some time trying to take photos of the warblers at the lake, but they proved to be extremely difficult to photograph. Here’s the best shot I could get of one of the 2 Black-browed Reed Warblers.

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And this was the best I could get from the Pallas’s Grasshopper Warbler. They acted so different from last year when I could get many good shots of both species.

 

LBJ Watch

On the morning of 20 February 2013, saw me birding along the boardwalk around Chiang San Lake, Chiang Rai. The lush vegetation surrounding the lake was filled with plenty of warbling songs since most of the migrating warblers were already in their spring migration mode and were beginning to sing their hearts out. At least 2 Pallas’s Grasshopper Warblers were spotted and it was the first time for me to really get some decent shots of this elusive species.

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Out of all the shots that I took that morning, this was my most favourite. It perfectly shows the lush habitat where the bird was dwelling in a very pretty lighting condition.

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Even though the birds were unusually showy for their standards, they were still considerably shy.

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It was also the first time for me to hear their unusual song. You can listen to the song here.

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I really had a great time watching and taking photos of them. Locustella warblers are definitely my most favourite group of warblers. Recently, the Asian members of Bradypterus have also been moved into Locustella as well.

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Asian (former) Bradypterus and Locustella warblers both share some major characteristics such as long undertail coverts, similar bill and body structure, as well as overall behaviour. The Asian members of Bradypterus also look much different from their African counterparts. That’s why I also agree with the recent change in taxonomy.

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Showing the streaked mantle and rusty uppertail coverts.

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Another species of warbler that was showing equally well or even better around the lake was the Black-browed Reed Warbler. There were 3-4 birds singing and chasing each other in the same area where I was photographing the grasshopper warbler. At times, they would come even closer to me than the grasshopper warblers but I was focusing so much at the grasshopper warblers that I ended up having just a few photos of the Black-browed Reed Warblers.

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I definitely have to go back there again when I get back to Thailand in March. This should be the prime time for taking photos of these LBJs since they’d be even more vocal and showy. Hopefully, there will be some other species and I will have more time to spend around the lake as well.