In mid-May 2011, I found and digi-scoped two adult male Common Rosefinch Carpodacus erythrinus on the Yellow Sea island of Eocheong. Although “red male” Common Rosefinch are scarce in the Republic of Korea (ROK), the first (on May 13th) seemed fairly unexceptional (red-headed, with obvious brown admixed into the reddish tones on the upperparts). The other, found on May 14th (a day with a large-scale arrival of birds arriving from the northwest), was far more striking: a beautiful deep red on the head and breast; red or reddish on most of the upperparts; and pink across much of the underparts.
As part of ongoing work for the Birds Korea Gallery and Checklist (which lists grebnitskii as the only Common Rosefinch subspecies so far recorded in the ROK), I recently sent a couple of images of this more colourful bird to Arend Wassink (founder of the wonderful “The Birds of Kazakhstan” website, at: http://birdsofkazakhstan.com/). I asked him about subspecies identification, and he replied (on June 20th) that to him the May 14th bird showed several “good characters” of roseatus.
Identifying Subspecies
According to Svensson (1992) adult male Common Rosefinch can be safely separated from red Second calendar-year males by the colouring and condition of the wing-feathers and wing-coverts. Both of the Eocheong males showed pink or red fringes and wing-covert bars (not white or off-white as in Second Calendar-year birds), and did not look particularly worn. Both are therefore assumed to be adult. The striking plumage differences between these two birds are therefore not a result of a difference in age between them. They instead appear more to be a result either of individual variation or more likely due to differences found between subspecies.
Although details on biometrics and plumage differences can be found in the specialist literature (little of which is available to us here), online information on differences between the various subspecies of Common Rosefinch appears to be limited. One source (http://www.birds.kz/species.php?species=614&l=en) describes grebnitskii as darker red on the mantle, throat and breast and darker pink on the belly and flanks than the nominate subspecies, with a thicker and more massive bill than other subspecies. Roseatus is not described. Pavlova et al. (2005) do not provide details on plumage on any of the taxa, but instead cite a range of publications and conclude that:
“variation of the common rosefinch is reflected in the relative intensity of the red and pink colors, and body size (Cramp and Perrins, 1994; Dement’ev and Gladkov, 1954; Stepanyan, 2003). Based on this external phenotypic variation, either four (Dement’ev and Gladkov, 1954) or five (Cramp and Perrins, 1994; Stepanyan, 2003) subspecies are recognized. Subspecies descriptions are quantitative, which causes inconsistencies in descriptions of subspecies’ ranges by different authors”.
While size is not possible to assess (though the bird on May 14th initially appeared to be quite massive-looking), the images show that the brighter of the two birds has much more intense and extensive red and pink. While there are some traces of brown on the scapulars, the mantle is red (striped darker) and the back and rump are also solid red. The underparts too are saturated with pink, most intensely on the lower breast and belly, but extending more palely-across the vent too. This intensity seems to either match or even exceed the few images of roseatus that I have so far been able to find online.
The May 14th bird therefore appears to be out of the plumage range of grebnitskii which, as depicted by Brazil (2009) and as described by other sources, has brownish upperparts, admixed with red (like the bird of May 13th). It instead shows several good characters of roseatus. But although it seems to look like a roseatus, just how likely is one as far east as the ROK?
Distribution of Common Rosefinch subspecies
Described as a breeding species in north-eastern DPRK (Tomek 1999-2002), the Common Rosefinch was only first-recorded in the ROK in 1965. By the beginning of this century, there had still been only eight records involving 15 individuals in the ROK (Park 2002). With an increase in observer activity, however, the Common Rosefinch is now known to be a regular though fairly uncommon migrant here, most frequent on Yellow Sea islands from late April to mid-May and again in September and October. In common with many species that breed on the Asian mainland (especially to the northeast of Korea) but not in Japan, the species is commoner northward. For example, peak day counts on Socheong Island (of four during northward and 58 during southward migration: Moores 2007) are much higher than on the southern island of Gageo, where there are seldom more than one or two at peak. The species remains rarely-reported on the mainland, though several of these mainland records have been in mid-winter.
Up to now, all Common Rosefinch in the ROK have been assigned to subspecies grebnitskii. This is presumably based largely on range descriptions provided by authors outside of Korea, though has perhaps also been supported by in-hand measurements of a few individuals.
Based on the limited literature available to us, subspecies grebnitskii is indeed the most likely subspecies to occur in Korea. Breeding in northeast Asia and wintering southward, it was the only subspecies recorded in Japan (Brazil 1991). More recently, Brazil (2009) stated that grebnitskii is found in “NE China and N. Korea to Sakhalin, NE Siberia and Kamchatka” (with the nominate subspecies found much further to the north and west). Cheng (1987), on the other hand, earlier mapped only two subspecies in China: grebnitskii and roseatus, with the former distributed in north-east China (and northward) and the latter with the centre of its breeding distribution far to the west of Korea, in Qinghai east to Shaanxi. Intriguingly, however, he also described roseatus as a migrant as far east as Hebei and Shandong provinces (Cheng 1997). The map in Pavlova et al. (2005) is perhaps intentionally a little less clear: while the Common Rosefinch is mapped across much of the region, the ranges of the various subspecies are not well-defined. Nonetheless, subspecies grebnitskii is indicated as occurring far to the north-east of Korea; nominate erythrinus far to the north-west; and roseatus, as a breeder which seems to reach as far east as Shanxi or even south-western Hebei. Based on the range given in Cheng (1987) and in Pavlova et al. (2005), and on records of many other migrant bird species, roseatus therefore seems quite likely to occur in the ROK - though probably rather (or very much) more rarely than grebnitskii.
Lacking adequate experience in these taxa, we are looking for informed comment on the identification of Common Rosefinch subspecies.
As always, thank you in advance for you comments, information on biometrics, opinions and images!
References
- Brazil, M. 1991. The Birds of Japan. Published by Helm.
- Brazil, M. 2009. Birds of East Asia. Helm Field Guides.
- Cheng T-H. 1987. A synopsis of the avifauna of China. Beijing: Science Press, and Hamburg and Berlin: Parey.
- Moores, N. 2007. Selected Records from Socheong Island, South Korea. Forktail 23: 102-124.
- Park, J-Y. 2002. Current status and distribution of birds in Korea. Department of Biology, Kyung Hee University, Seoul (unpublished thesis, in Korean).
- Pavlova,A., Zink, R. & S. Rohwer. 2005. Evolutionary history, population genetics and gene flow in the common rosefinch (Carpodacus erythrinus). Molecular Phylogenetics and Evolution 36 (2005) 669-681.
- Svensson, L. 1992. Identification Guide to European Passerines. Fourth Edition.
- Tomek, T. 1999-2002. The birds of North Korea. Acta Zoologica Cracoviensia 42: 1-217; 45: 1-235 (in English).