Nial Moores, February 8th 2013.
Work on revising the Birds Korea Checklist continues, and as on previous occasions multiple questions remain, even about some widespread species.
The Olive-backed Pipit Anthus hodgsoni is one such species. It is a common migrant (with a peak day-count of several thousand one year on Eocheong); a scarce and probably very local breeding species (confirmed on Jeju and strongly suspected at one or two mainland sites); and also a winter visitor – most especially to the south-east (e.g. 25 in one small park in Busan on February 7th 2013 was notable but hardly remarkable). The challenge with Olive-backed Pipit is: to which subspecies (singular or plural) do “our” birds belong?
Several references suggest that perhaps both yunnanensis (a common summer visitor to the north and northwest of the Korean Peninsula) and nominate hodgsoni (which breeds as close as Japan) both occur. And some, like Alström et al. (2003), also allow that there is in addition an unclear zone with intergrades. The map on p. 148 in their study shows this area of intergradation as Hokkaido – while also excluding the ROK from the world distribution of the species! According to the same authoritative source, hodgsoni and yunnanensis are for the most part “rather easily separable by plumage”, due to hodgsoni showing “more heavily streaked central crown and, especially, mantle and scapulars…sometimes shows slightly paler stripes on the sides of the mantle…The streaks on the breast are on average bolder…and on average reach further down the belly. The flanks are usually heavily streaked…The dark patch on the ear-coverts is on average larger and more prominent” (Pp. 142-143).
While appealing to birders for images of Olive-backed Pipit (especially from Japan, northern China and Russia), so we can get a better understanding of what the range of plumage might be from different parts of the range, here are a few images from yesterday (February 7th). They are of several individuals in a mixed group of over-wintering birds in Busan, ranging from lightly to rather heavily streaked.
Fig. 1 Putative yunnanensis: even though worn, showing only weak streaking on the mantle, fairly plain scapulars and weakly-streaked flanks.
Fig. 4 Putative hodgsoni (or at least not pure yunnanensis!) showing strong upperpart streaking (extending up on to the central crown) and also strong flank streaks, just visible on the left side of the bird.
Alström P. Mild, K. & B. Zetterström. 2003. Pipits & Wagtails of Europe, Asia and North America. Helm.