In mid to late October 2005, an unexpected number of forest species appeared to be present on Socheong Island, with several of these species previously unrecorded on the island (where autumn raptor surveys in 2002 were followed by raptor and passerine counts in 2003 and 2004). There were several records of Chinese Nuthatch Sitta villosa, and one Eurasian Nuthatch Sitta europaea for example, as well as many “Great Tit” - either Eastern Parus (major) minor or Parus major - and Eurasian Jay Garrulus glandarius brandtii, single Great Spotted Woodpecker Dendrocopos major and even two or more Hazel Hen Tetrastes bonasia!
On October 21st, a cold front moved through the area, with a few hours of rain and subsequent very strong north-westerly winds (peaking at Beaufort 8-9), which gradually moderated on the 22nd, when the maximum temperature reached only 13 C. There was a significant movement of Siberian Accentor Prunella montanella on the 22nd (ca 50 logged by the four observers present), along with a broad range of other migrants, including yet another new forest species for the island (and Korea): a Yellow-bellied Tit Parus venustulus!
In the late afternoon, of October 22nd in a relatively sheltered but still breezy, sunlit valley in the centre of the island, Nial Moores was watching single Pallas’s Phylloscopus proregulus and Two-barred Greenish Warbler Phylloscopus trochiloides plumbeitarsus, which were then loosely joined by a small group of five or so fast-moving Coal Tit Parus ater.
In amongst this group, a very small and brightly colored bird was glimpsed through the foliage. The combination of its bright yellow underparts, white cheek patch and strong double wing-bar immediately suggested Yellow-bellied Tit, a species previously unrecorded in Korea (and apparently outside of China?), but which Nial Moores had seen several times in Beidaihe back in spring 1992.
On these brief initial views (lasting only 2 seconds or so, at 30 m range), the head pattern appeared very contrasting black and white, and it was thought to be an adult male. Waiting nervously in the same spot for a confirmatory view, several more groups of tits and warblers moved through the sunlit patch, with many more moving further down the valley – but the Yellow-bellied Tit did not show itself again. After five very long minutes or more, Nial Moores then decided also to move down the valley some 50 m, and again soon caught sight of a small brightly-colored tit flitting deep in the foliage of a single, taller, sunlit tree. Although it soon dropped out of view, it fortunately returned quickly to the same tree, where it then fed actively, using its proportionately strong bill on a couple of occasions to hammer at seeds, held between its feet: strikingly different feeding behavior to the finer-billed Coal Tit it loosely associated with. On these longer views (totaling 30 seconds or more over 3 or 4 minutes), the yellow underparts (paling towards the vent), the dark upperparts, with an obvious though slightly diffuse-edged pale nape-patch, the double wing-bars and the extensive white cheek-patch were all well-seen and a series of handheld digi-scope images were taken.
On these longer views the head pattern appeared rather less contrasting than when seen initially (suggesting the possibility of it being a different individual), with some greeny-grey mixed into e.g. the crown, and a small whitish patch above the eye. In addition, the bird lacked an obvious bib, instead having very obvious dark smudges in the malars, forming a larger patch more distally, while the bill showed obvious paling towards the base. Reference to e.g. Mackinnon and Phillipps (2000) suggest that the bird was most likely a first year male.
Having secured images, Nial Moores then found Koshiyama Yozo and led him to the spot, in the hope that he could also see the bird, but the sun light had already weakened somewhat and despite some intensive searching, it could not be found.
On the morning of the 23rd, in clear conditions with only light winds, the area was checked again, again unsuccessfully. On that day there was a very large movement of “Great Tit” with at least 500 logged on the island by Nial Moores alone, including a single group of 150 at the lighthouse trying to head out to sea. It seems fairly likely that the Yellow-bellied Tit moved off the island at this time, as further searches for the bird on 24th and 25th also proved unsuccessful.
Mackinnon and Phillipps (2000) suggest that Yellow-bellied Tit is “subject to periodic irruption”, while it has been considered by some observers to be a partial migrant in the north of its range. E-mail communication with Leijinyu of the Beijing Bird Watching Society in early November suggested that there had apparently been no exceptional numbers of Yellow-bellied Tit reported in North-east China in the autumn of 2005, so it was assumed that this was a rather exceptional one-off record, likely drifted across the Yellow Sea by the gale-force northwesterly winds on the 21st.
However, on November 13th 2005, Peter Nebel and Jake Maclennan then also found a Yellow-bellied Tit - this time in Eunpa Park in Gunsan, several hundred km to the southeast of Socheong - thus Yellow-bellied Tit became yet another “double-first” for South Korea (recalling the unexpected discovery of Scaly-breasted Munia Lonchura punctulata on Socheong in 2003, followed very soon after by a flock on Hong Island).
Initial descriptions of the Gunsan Yellow-bellied Tit indicate it was a non-breeding plumage male:
“It was about 4:45pm, partly cloudy, about 10C., with sunlight coming in at between 60 and 90 degrees. The distance was on the order of 30m, possibly a bit farther.
To be honest, I was looking for a Coal Tit and was surprised when this bird looked yellow underneath and even after looking at it for a few seconds it continued to be yellow, so it wasn’t a light artifact. At that point, I started really examining it and realised that the throat was yellow, as well, and bordered by black malar-type stripes. My memory of the crown was that it was black, because the head gave the impression of a Coal Tit, except for the throat. Once I realised that I had something truly different, I got Jake looking at it, and I think he saw more of the detail on the back than I did. We must have watched the bird for 2-3 minutes” (Peter Nebel, in lit, Nov 2005)
“in a copse of trees east of Eun-pa Park among a large group of mixed Tits a single Yellow-bellied Tit was watched well enough that it showed all its field marks. The bird had a strong double wing bar, a stripe up the nape, yellow extending from the belly up to or near the throat. That is, the tit lacked any bib, but PN noted malar marks. It was observed at relatively close range.” (J. Maclennan in lit., Nov 2005).