Here in the Republic of Korea (ROK) a large movement of Varied Tit Poecile varius started in late August. On August 26th and again on 29th, a group of us watched several small groups spiralling up and dropping back down again into cover on Heuksan Island (34° 41′ N 125° 28′ E), an island some 500km north-east of Shanghai. This is an island with a breeding population of the species – but this type of behaviour was notably unusual. Back on the mainland on August 31st in Mokpo City (at approx. 34° 47N, 126° 23 E), where Varied Tit is a common resident, we then saw >50 moving west in only 15 minutes, with some birds first landing on overhead wires above us before flying off westwards, and others already probably >200 metres above sea-level and still climbing (as typical for tits during “proper movements”). A small westward movement of Varied Tit (several groups of 4-5 birds) was also seen in Gunsan, >150km further north, both the same day and on September 1st.
This movement was not limited to the ROK. In Japan, Chris Cook reported to the Kantori Listserver that on August 31st in the Japanese Alps (on Honshu) “in a matter of a few hours, there were probably 100 [Varied Tit] or more in small groups — 5, 10 or even 20 — passing west”. Later, on October 2nd, Hiraoka Takashi of the Yamashina Institute reported to the Oriental Bird Club Listserver that the species was also being seen, unusually, in central Tokyo and Osaka. Abiko town, Chiba, seemed also to be having its best year for the species since 2006…
Back in the ROK, 1000km west of Chiba, tens of Varied Tit showed irruptive behaviour most days both in Busan (at approx. 35° 06N, 129° 02 E), and in nearby Gimhae, through until late September at least. On days with fieldwork, small groups of Varied Tit, increasingly accompanied by Coal Tit Periparus ater, flew out south to sea, and then moved off southwest. On October 3rd, four of us even watched a Varied Tit circling our small boat, 10-15 km offshore from Busan. It then either headed towards the Japanese island of Teima Do / Tsushima or on to the ROK, calling as it went. At the beginning of October too, flocks of up to 15 were found on Socheong Island (37° 45′ N 124° 44′ E), 490km to the north-east of Busan, on an island where the species is usually uncommon or even absent.
With such high numbers across much of its range and obvious westward movement, it seemed likely that at least some of these Varied Tit would also make it into eastern China. And, according to the Oriental Bird Club Listserver and China-birders Jesper Hornskov et al., this has happened. In the past few weeks there have been first records of Varied Tit in Zhejiang Province / Shanghai (first from September 15th), in Hong Kong (late September), in Shandong Province (on October 1st) and in Beijing Municipality (first on October 3rd).
Occasional mass movements of species in autumn and winter (“irruptions”) are to be expected in this region. The Republic of Korea (ROK) lies to the south of a broad expanse of cold temperate and boreal forest. Some years, there is abundant food, and in other years there is a shortage. Dependent on high bird density in relation to food availability across and within subregions of this vast landmass, some species then need to move – bringing them some years down onto the Korean Peninsula. For some species at least, unusually high numbers here seem also to coincide with strong northerly or north-westerly winds in late October / early November. These winds presumably drift a larger than average number of birds down the peninsula.
According to the excellent review by Newton (2006):
Irruptive “migration occurs in populations that breed in areas where food is plentiful in some winters and scarce or lacking in other.” Affected populations of “irruptive seed-eaters and rodent-eaters can travel hundreds or thousands of kilometres between the breeding areas used in different years. They can also spend the winter in widely separated areas in different years, up to several thousand kilometres apart…”
As in other regions, irruptions into (and through) the ROK are comprised largely of forest-dependent species – including titmice, nuthatches, Eurasian Jay Garrulus glandarius, finches and rosefinches, and to a lesser degree Eurasian Treecreeper Certhia familiaris, Great Spotted Woodpecker Dendrocopos major, thrushes and some species of raptor. Examples of irruptive behaviour include the one day-estimates of 10,000 Coal Tit Periparus ater on Socheong Island (compared to the more usual dozens) in both October 2003 (by Nial Moores) and 2010 (by Shim Kyu-Sik and Kwak Ho-Kyung); the widespread records between November 2007 and February 2008 of the normally-scarce Eurasian Treecreeper; and the tens of Rough-legged Buzzard Buteo lagopus present along the east and west coasts, also in the winter of 2007 / 2008.
Once here, and especially once the main migration period is over, the Korea Peninsula’s geography (with sea on all three sides), the relative abundance of forest-habitat and the generally milder climate compared to more northern regions, then tends to keep many of these birds in the ROK through the winter.
Although we are still in early-mid autumn, the winter of 2012 / 2103 therefore already seems much more promising than the extremely bird-poor autumn and winter of 2011 / 2012. In addition to the movement of Varied Tit, this also looks to be a great winter-to-come for Chinese Nuthatch Sitta villosa. The Chinese Nuthatch, a pine-forest specialist which breeds fairly commonly in the DPRK, is absent or near-absent in the ROK most winters. The “record-breaking” irruption in 2005 / 2006 involved only ten or so individuals, almost all in Incheon, between October 11th and April 3rd (See http://www.birdskorea.org/Birds/Birdnews/BK-BN-Review-2005.shtml). This autumn, Chinese Nuthatch was apparently first recorded in Incheon on September 26th. Since that time, there have already been further records in Song Do and Yeongjong by Spike Millington, and an estimate of 15-20 in one day seen by Shim Kyu-Sik on Socheong Island on October 2nd. Interestingly, the 2005 / 2006 winter also saw the first national records in the ROK of Yellow-bellied Tit Periparus venustulus, another coniferous forest specialist. This species is increasingly recorded and has apparently even bred here in the ROK. It is probably also present in the DPRK (although there are / were no official records, a 2010 documentary on a visit to Pyongyang broadcast recently on ROK TV contains a sequence with what appears to be a Yellow-bellied Tit calling in the background!). With this increase, it is perhaps no surprise that the 12-15 reported on Socheong on October 1st by Subjohit Chakladar now becomes the highest known day-count of this species in the ROK known to Birds Korea (see https://www.birdskoreablog.org/?p=6283). Not taking anything away from the ROK high-count, this number still compares quite poorly with the 112 recorded in the Beijing Botanical Gardens by Jesper Hornskov on October 4th! With one Yellow-bellied Tit in Busan on October 5th and the first record for Mara Island off Jeju this autumn too (via Shim Kyu-Sik and Kang Chang-wan), perhaps these are the kind of numbers we can look forward to in future autumns?
Intriguingly, neither Varied Tit, Chinese Nuthatch nor Yellow-bellied Tit breed much further north than the Korean Peninsula. They do not belong, therefore, with the more typically irruptive, northern species of boreal forest. Moreover, in Beijing other species “on the move” at present appear to include two species that should be distributed much further to the south still: Scaly-breasted Munia Lonchura punctulata and White-rumped Munia Lonchura striata (via Jesper Hornskov). The former species was first recorded in the ROK in October 2003 and the latter species has yet to be claimed here.
Either way, if previous years are any guide, we should soon know – within a few weeks at most – what kind of a landbird-winter we can expect.
We would therefore like to ask if you can help us to track this autumn’s irruptions across the ROK and East Asia. Please share your records of irruptive species (with species name, location, date and number) either in English or in Korean, either by sending an email or by posting as a comment below this blogpost.
With thanks in advance, and in the hope of a wonderful winter of birding!
Newton, I. 2006. Advances in the study of irruptive migration. Ardea 94(3): 433–460.