by Craig Brelsford
Shanghai Birding is the WeChat companion to shanghaibirding.com. In it, we exchange real-time reports and engage in discussions about birding in Shanghai and all China.
A discussion about Arctic Warbler showed the utility to birders of social media in general and Shanghai Birding in particular. Members Jonathan Martinez (based in Shenzhen) and Paul Holt (based in Beijing) shared their knowledge about Arctic Warbler and its sister species. In so doing, they shed light on the situation, still very imperfectly understood, of the Arctic-type complex in Shanghai.
Holt led off:
Paul Holt (PH): I see from a recent posting that @李伟 photographed an Arctic Warbler at Nanhui on the 28 October. Great images! Isn’t that extremely late? The latest ever Beijing record’s over two weeks earlier than that.
I then posted a long list of my Arctic-type records from autumn 2014 and autumn 2015. In the list, I bunched together all members of the Arctic Warbler Complex (Arctic Warbler Phylloscopus borealis borealis and P. b. kennicotti, Kamchatka Leaf Warbler P. examinandus, and Japanese Leaf Warbler P. xanthodryas). I list all three species because, although it is presumed that the majority of spring and autumn records in Shanghai are borealis, it is far from certain what the proportions are. (Arctic Warbler and its sister species are nearly impossible to separate on morphology but are distinguishable by voice.)
The latest autumn record I had of an Arctic-type warbler was 24 Oct. (2015).
Holt wrote back:
PH: Thanks @Craig (大山雀) Unless I’m missing something 28 October is later than any of the records you cite (but just by four days). Could it be that the Nanhui sighting is Shanghai’s latest ever? Also it’s interesting that you mention all three species. Have any of your region’s Arctic-types been identified to a species other than borealis?
Craig Brelsford (CB): @Paul Holt I have not recorded anything other than borealis around Shanghai. (All confirmed borealis records are of individuals singing in spring.) I also suspect that a record of xanthodryas is next to impossible in Shanghai. I am aware that citing all three names is not a perfect solution. I list all three species because I believe information is insufficient. No one knows how many Arctic-type in Shanghai are borealis and how many examinandus. Very basic facts about the species in east-central China are unclear. Maybe someday studies will confirm that an Arctic-type in east-central China is borealis, with a probability of 99%. In that case, I would probably assign any silent Arctic-type I saw to borealis. Do you have any suggestions?
A few minutes later, I added:
CB: Just remembered that Michael Grunwell, Elaine Du, and I had Arctic-type this past Sat. 5 Nov. We got a good look at the bird, too. October was a warm, wet month in Shanghai, and the entire fall migration season seems to be late a week or two. Would others here agree?
PH: I’ve never seen xanthodryas in mainland China, have only ever encountered two examinandus (which were the first records for Liaoning & Hebei. Both sound recorded) here & have too little to go on I’m afraid @Craig (大山雀). Personally I log everything as Arctic Warbler by default, though that’s far from perfect. Until more of us work on this awkward group & make an effort to sound-record them, it’ll be a long time yet before a truer picture of their patterns of occurrence emerges. Cracking late record last weekend @Craig (大山雀). Surely that must be a good candidate for being the latest ever.
CB: @Paul Holt Maybe for simplicity’s sake I should log everything as Arctic. I have hesitated because I dislike speculation, and besides your very reliable records from up north I have little else to go on.
At this Martinez came in with his south-China perspective:
Jonathan Martinez (JM): I’ve heard xanthodryas on Fujian coast in early May and had a bird caught in October at Xitou identified as xanthodryas by DNA on tail feathers among about 15 borealis. I found an examinandus in central Guangxi in September, first suspected by call on a bird wave and clearly identified with call a few days later. I suspect examinandus is not a coastal migrant and probably goes through mainland China. I think still the only species recorded in Hong Kong is borealis, despite many looking for these.
CB: Thanks! With a confirmed xanthodryas in Fujian and examinandus only “suspected” not to use the Chinese coast, I’ll keep my clunky three-species listing. Arctic-type Warbler in China is a subject crying out for more research.