Daily Archives: 17/05/2022

Baekryeong Island, April 30~May 8

Bird news from Subhojit Chakladar (with Dr Nial Moores, Andy Lee and Justin Lee)

NOTE: This post was substantially modified following input from Prof. Per Alstrom between May 20th and 23rd.

Peak of the spring migration on this island is a delightful experience. This year however, birds seemed to be in reduced numbers partly due to the wind direction and intensity, and probably partly due to unusually cold temperatures in southern China. Compared to last year, most of the days the diversity of species and numbers seemed much less (185 species observed in 2021 from May 1~9, compared to 172 species this year). There was only one single day where birds were seen moving in significant numbers.

April 30

Arriving on the island at around mid day, I met up with NM and we birded the main wetland and the western part of the island. A Pied Avocet and a very unseasonal Tundra Swan were the highlights of the day. A Great Bittern was also heard booming.

The eBird checklist for the day can be found here.

Pied Avocet, Recurvirostra avosetta © Subhojit Chakladar
Tundra Swan Cygnus columbianus 고니 © Nial Moores

May 1

We continued to focus on the western part of the island. 92 species were spotted which would be a good number for any island region in the country but was rather slim pickings by the standard of the island given the time of the year. Swinhoe’s White-eye, which is almost exclusively confined to the outer islands in Korea, were seen in good numbers including a flock of around 35 individuals.

The eBird checklists for morning and afternoon sessions.

Swinhoe’s White-eye Zosterops simplex 작은동박새 © Nial Moores
Eastern-crowned Warbler, Phylloscopus coronatus © Subhojit Chakladar

May 2

This was the only day where we could observe movements on any significant scale. The morning session was spent almost exclusively in the north-eastern part of the island watching (and at times counting) the moving birds. Good number of buntings were on the move with Yellow-browed Bunting being the majority followed by Little Bunting and Black-faced Bunting. Good numbers of Chinese Grosbeak, Olive-backed Pipit and Eastern Yellow Wagtail were also on the move. Mixed groups of snipes were also seen flying around with some of them settling down in the reedbeds as the wind picked up from the north. All 4 species of snipe that migrate through Korea were observed. Breeding plumaged Chinese Penduline Tit were busy feeding. Single Pacific Golden Plover and White-throated Needletail were also seen in flight, while Japanese Quail was heard singing and later flushed from a grassy trail.

The eBird checklist for the day can be found here.

Chinese Penduline Tit, Remiz consobrinus © Subhojit Chakladar
Little Bunting, Emberiza pusilla © Subhojit Chakladar
Yellow-breasted Bunting, Emberiza aureola © Subhojit Chakladar

May 3

AL after having arrived the previous day, joined SC and NM. We hit all the major birding spots on the island with close to a 100 species spotted. New birds for the trip was a Wryneck, a couple of Asian Stubtail and a White-shouldered Starling.

The eBird checklist for morning and afternoon.

Eurasian Wryneck, Jynx torquilla © Subhojit Chakladar
Pale-legged Leaf Warbler, Phylloscopus tenellipes © Subhojit Chakladar
Radde’s Warbler, Phylloscopus schwarzi © Subhojit Chakladar

May 4

An Alpine Leaf Warbler was the highlight of the day. JL arrived by mid day and joined AL and SC for the afternoon session of birding.

The eBird checklist for morning and afternoon.

Alpine Leaf Warbler, Phylloscopus occisinensis © Subhojit Chakladar
Brown Shrike, Lanius cristatus © Subhojit Chakladar

May 5

The Alpine Leaf Warbler was still hanging out in the same group of trees.

However, the highlight of the day was a “golden spectacled warbler” first seen by SC and poorly sound recorded. For the next 4 hours, all members of the team were able to get a visual of the bird though it remained rather out of reach for good photos. At first view, the bird appeared to have a striking head pattern with the grey in the crown being clearly demarcated from the greenish tones of the ear covert. The underparts appeared rather bright yellow. Observed from a distance, the bird seemed to have quite a heavy bill with the lower mandible being almost completely orange.

JL (very skillfully) managed to get a few record shots of the bird as it perched momentarily in view amongst the dense tangle of vegetation that it kept to. Even though the shots were distant (and not fully focused given the difficult conditions), the photos still highlight some of the distinct characteristics of the bird. Given that the “golden spectacled warbler” complex can be extremely similar looking, most literature emphasizes that the only reliable way to distinguish them in field is by their calls and songs. Sometimes, it’s easier to “visualize” such calls in spectrograms. Certain species (Pale-legged and Sakhalin Leaf Warbler for example) have similar sounding calls but the frequency range of the calls as seen in a spectrogram don’t overlap.

Below is the call, which mostly sounded flat but which generally sounded squeeky, and occasionally included a more, slightly rolling complexity.

Call recorded on a Zoom H1N recorder and cleaned up © Subhojit Chakladar

The call of this “golden-spectacled warbler” can be visualized via a spectrogram, as shown below

The call shows up as “chirps” in the 3~5KHz region.

Based on visual observation alone, the bird could have been any of the 4 species of “golden spectacled warblers”. However, the call and its frequency distribution at least helps exclude Alstrom’s Warbler (bisyllabic call) and Bianchi’s Warbler (non-overlapping frequency range). This narrow’s it down to either Grey-crowned Warbler or Martens’s Warbler. Having been a witness to last year’s Martens’s Warbler and analysis of the call, differences detected between calls between years (apparently!) left Grey-crowned Warbler as the strongest possibility.

We shared the recordings with Dr Jungmoon Ha, who compared them to recordings of Marten’s and also of Grey-crowned Warbler by Bram Piot in Laos (XC625377). Both the pattern and frequency range of the Baekryeong bird seemed to match the latter.

The bird was therefore identified, after days of discussion, as a Grey-crowned Warbler based on this evidence and the photos below. Independent verification (or refutation!) of the ID, as for all hard-to-ID national rarities and potential firsts, was then sought through email.

Contra to our expectations, on May 20th and 21st, top expert Professor Per Alstrom replied in brief: “the call sounds like omeiensis…The quality of the recent bird by Justin Lee are exceptionally poor, but I would say that they stronhgly (sic) support omeiensis over tephrocephalus.” In a follow-up mail he added that, “omeiensis sometimes doubles its call, creating a ”double band” on a sonogram” – a major part of our confusion in the field, and in the sonagram.

This therefore becomes only the second national record of Marten’s Warbler P. omeiensis in Korea found for a while in very the same bush as the first, discovered last year!

Incidentally, Grey-crowned Warbler was reported from nearby Socheong Island by National Migratory Birds Center in May 2021 based on visual record only. In his latest mail, Per Alstrom supports the ID of that bird as Grey-crowned on the basis of a single image we provided to him.

The eBird checklist of the day can be found here.

Marten’s Warbler © Justin Lee
Marten’s Warbler © Justin Lee
Eyebrowed Thrush, Turdus obscurus © Subhojit Chakladar

May 6

With fog blanketing the island for most of the day, birds were greatly reduced in numbers. Despite searching for the “Golden Spectacled Warbler”, we failed to relocate the bird.

Sharp-tailed Sandpiper, Calidris acuminata © Subhojit Chakladar

May 7

With the fog dissipating and winds picking up, birds were on the move once again. However, the strengthening winds made it difficult to bird and also kept birds in cover. A Daurian Starling gave good views while the number of Brown Shrike seemed to have increased a bit. The presumed Grey-crowned Warbler was heard briefly once again in the same area but we didn’t manage to get a visual. New birds for the trip were Sand Martin, Mugimaki Flycatcher, White-breasted Waterhen, Spotted Redshank, Purple Heron, Amur Falcon and Siberian Thrush. Early afternoon, a decent number of snipes were also seen in wet fields with at least 3 different species being identified. Buntings and flycatcher numbers were also picking up in the south-west of the island. The highlight of the day was a presumed Plumbeous Water Redstart seen briefly by SC.

The ebird checklist for the morning and afternoon sessions.

Chestnut Bunting, Emberiza rutila © Subhojit Chakladar
Daurian Starling, Agropsar sturninus © Subhojit Chakladar
Forest Wagtail, Dendronanthus indicus © Subhojit Chakladar
Purple Heron, Ardea purpurea © Subhojit Chakladar
Japanese Sparrowhawk, Accipiter gularis © Subhojit Chakladar
“Swintail” Snipe based on the underwing pattern, relatively short bill and feet projection beyond the tail © Subhojit Chakladar

May 8

We spent the final day on the island once again focusing on the western part. Highlight of the day was a Yellow-streaked Warbler (heard by NM in the morning and later by AL).

On the ferry back, about a dozen Streaked Shearwater, a heavy set Loon in flight and 2 flocks of Ancient Murrelet.


Thanks to Prof. Per Alstrom for confirming the ID of this bird; Dr Jungmoon Ha for very gracefully sharing the analysis of the sonograms; and Justin Lee for skillfully capturing the images under really difficult conditions.