On 1 June 2021, Beijing resident, Colm Moore, found Beijing’s first Kamchatka Warbler (Phylloscopus examinandus, 堪察加柳莺 Kān chá jiā liǔ yīng) at the Ming Tombs Reservoir in Beijing. It is the latest in a series of excellent records from Colm, crowned by the astonishing record of a Streak-throated Swallow (Petrochelidon fluvicola 彩石燕 Cǎi shíyàn) at Shahe Reservoir in May 2014 which was not only a first record for Beijing but also for the whole of China!
Colm is one of the best birders I know and also one of the most genuine guys around. This is his account of the incredible find on 1 June.
By Colm Moore.
More than half a decade ago, on Professor Per Alström’s advice, I began the slow, laborious process of recording Beijing warbler songs in some systematic manner. This was solely to further my own meagre knowledge and in order to make sense of the plethora of spring song from that myriad of phylloscopid taxa we hear and see each year. Per’s breakthrough work (Alstrom, P, et al., Ibis (2011), 153, 395–410) on the three “borealis” sibling species, Arctic Warbler P. borealis, Kamchatka Leaf Warbler P. examinandus and Japanese Leaf Warbler P. xanthodryas was on my desktop but surely an academic exercise, and not for the field….. surely.
Six years later, almost to the day, I crept into the woodland of pollarded Salix at Ming Tombs Reservoir’s Flower Garden to record Arctic Warbler P. borealis and compare it with some earlier recordings. I carried a lightweight Sony PCM D100 digital recorder and enough water to last an eight hour vigil. Six years has taught me infinite patience.
Four days of light easterly breezes, a drier than usual Meiyu Low Pressure System and a waning gibbous moon meant that on 1st June, there were very few nocturnal migrant warblers present, but a mellifluous fall of Black-naped Orioles Oriolus chinensis also guaranteed that the trees were alive with an orchestra of sound. Against this background I could hear the ‘dzrt’ calls of a few Arctic Warblers and an occasional burst of song from the same species, transcribed here as ‘zezezezezezezezezezezezezeze’, increasing in strength mid-way and fading somewhat at the end. All other warblers had indeed vacated the area, apparently. Every phylloscopid sound was borealis-like in nature, all my photographs showed borealis-type birds apparently and so I settled down to listen and perhaps make a few decent recordings.
About two hours into the vigil, listening with too little deep attention to the ‘dzrt‘ and the high mechanical ‘zezezeze‘, like a dreamer awakening from a drowsy woodland sleep, I began to hear a distant stuttering call, ‘drt‘..’drrt‘, audibly underneath and beyond the rest. It had probably been present for hours. Still stupefied, I slowly rummaged for my recorder, with all the time in the world, apparently. Meanwhile the bird or the sound had moved to my right and a short strophe of pumping action phylloscopid song leaked out from behind an Oriole’s chortle. Galvanized, I swung around wildly to catch some precious phrase, stumbled upon the correction direction and there, 10s into the recording, was that unique harsh pumping action of an examinandus song, electronically captured, and transcribed in the field as: ‘zeze-zeh zeze-zeh zeze-zeh zeze-zeh zeze-zeh zeze-zeh zeze-zeh’. It was a rather rough, rapid, short series of notes with a regular pumping, pulsing rhythm. The pumping rhythm seemed to be caused by two different syllables ‘zeze’ and ‘zeh’ being repeated.
Minutes passed in exquisite breathless panic as I waited for the bird to sing again. But the shadow of a Black Stork Cigonia nigra, flying low over the wood now threw the place into silence and though the Orioles were undisturbed, the bird with that unique examinandus sound had departed or rendered silent. Hours and hours later I stumbled into the light, exhausted from combing the wood, leaf by warbler-shaped leaf, frequency by dizzy frequency. I had dozens of photographs of borealis-types, but I could not definitively match call with image. I even noted wing-flick behaviour in some, but again was unable to match behaviour with call.
Terry Townshend, to whom I sent the recording, was able to support my tentative identification as examinandus, and with his encouragement I sent the recording and all my photographs to Per Alström, who confirmed the song, saying:
…. I note that there’s a Kamchatka Leaf Warbler on your recording. First there’s a call which sounds like borealis, shortly afterwards is a call that sounds like examinandus (though I’ve heard birds which I thought were borealis on migration in SE China calling pretty examinandus-like, though I couldn’t be absolutely sure they were indeed borealis). However, at c. 10 s, behind an oriole is a very faint song strophe of a definite examinandus….. I see the odd wing flicking behaviour in one or two of your photos. I haven’t noted this in any ”Arctic Warbler”….. Something to check.
Colm’s original recording, with the call of Arctic Warbler (Phylloscopus borealis), followed by a two-note call that could be Kamchatka Warbler (P. examinandus), then the diagnostic strophe of song from Kamchatka Warbler (P. examinandus), with background Black-naped Orioles (Oriolus chinensis).
The taxon examinandus was first described by Professor E. Stresemann in 1913 but the morphological similarity to xanthodryas and borealis meant that it took a century to fully untangle the phylogenetic complexity of what are now considered three unambiguous clades, based on mitochondrial DNA, an analysis of songs and detailed morphometrics. But it became clear that for field workers, calls and songs were essentially the field evidence and recordings the tools by which to map the distribution of these sibling species. It has been established that examinandus breeds in south Kamchatka, Sakhalin and north-east Hokkaido. Likewise, among two-hundred sound-recordings in Xeno-canto (Xeno-canto Foundation and Naturalis Biodiversity Center 2005-2021: accessed September 13, 2021), winter-time records concentrate in S.S.E. Asia, specifically Indonesia. Passage migrants have been recorded in Japan, Nansei-Shoto, S.Korea and China. Remarkably, it has been recorded in Australia and in Finland (www.birdguides.com/articles/western-palearctic/kamchatka-leaf-warbler-in-finland-a-new-western-palearctic-species/).
Some records of the species on presumed passage, have come from as near to Beijing as Dandong, in Liaoning (Birding Beijing: accessed September 13, 2021), Tianjin (eBird Explore: Cornell Lab of Ornithology: accessed September 13, 2021) and coastal Hebei, with one recorded by Matt Slaymaker on 26 May 2013 and 1 June 2013 at the ‘prison trees’ at Nanpu, Tangshan (see https://www.xeno-canto.org/species/Phylloscopus-examinandus?pg=1). Thus the Beijing record is probably not wholly unexpected, given the geographical location of the capital, just west of the mapped migratory trajectory.
Big thanks to Colm for writing up his extraordinary find and for helping to raise awareness about this poorly-known species and its occurrence in Beijing. With greater awareness among birders, we can expect more records from the capital in future.
Title image: a ‘wing-flicking’ Phylloscopus, possibly the P. examinandus, from 1 June 2021 at Ming Tombs Reservoir (Colm Moore)