The new entries on the shanghaibirding.com list are Sakhalin Leaf Warbler, Dusky Warbler, and White-throated Rock Thrush. The new entries on the eBird list are those three plus Japanese Paradise Flycatcher and Taiga Flycatcher.
“Century Park is getting better,” Hiko said. My young friend is right. Century Park is an island of stability amid the sea of change (mainly degradation) that is the natural environment of Shanghai. Ten years ago this month, when Hiko was a tyke of 6, I made my first visit to urban Shanghai’s best birding area. Little has changed. The biggest difference between October 2007 and October 2017 is, the trees are taller. The wooded areas at Century have an ever-stronger woodsy feel.
— Century yielded yet another regional record of Sakhalin Leaf Warbler. Evidence is growing that in the Shanghai area this passage migrant has been neglected and is more common than previously thought. I recently wrote a series of posts, the latest being this one, on distinguishing Sakhalin Leaf Warbler from its sister species Pale-legged Leaf Warbler.
Here is the recording I made of the calling Sakhalin on Thurs. 5 Oct. Apart from a DNA assay, call as well as song is the only reliable way to separate Sakhalin Leaf Warbler from Pale-legged Leaf Warbler. At 4.9 kHz, the “tink” recorded below is a full kilohertz deeper than the call of Pale-legged Leaf Warbler.
— Eurasian Woodcock whizzed overhead on its way to Bird Island (31.217405, 121.554936). The woodcock was going to the one best place for it in the urban park. Bird Island, Century’s sanctuary-within-a-sanctuary, is a bird-friendly, cat-free parcel of woodland cut off from the rest of the park by a moat.
— Great Spotted Woodpecker used to be found mainly on Bird Island. On Thursday we found 2 in other sectors of the park. With the steadily improving woodland in the park, expect Great Spotted Woodpecker to be seen in more and more areas. Century Park is one of the few areas in urban Shanghai where woodpeckers are commonly found.
On Sun. 17 Sept. 2017 at Pudong’s Cape Nanhui, I achieved a personal first: photos of an unmistakable Sakhalin Leaf WarblerPhylloscopus borealoides. As expected, the photos show a leaf warbler whose plumage and bare parts are virtually indistinguishable from those of Pale-legged Leaf Warbler P. tenellipes. Coupled, however, as they are with sound-recordings of the same individual, ensuring the ID, the photos constitute a rare visual record of Sakhalin Leaf Warbler in Shanghai.
The leaf warbler I found was easily identifiable as a member of the Pale-Sak species pair. It had strikingly pale pink tarsi, an olive-brown crown contrasting with olive-green mantle and wings, a long and creamy supercilium, and faint wing bars on the median and greater coverts.
The bird, which was in Microforest 1, behaved in a way typical of the Pale-Saks I have observed in the Cape Nanhui microforests, eight tiny woodlands that dot the coastline of the cape. Rarely venturing more than 2 m off the ground, the leaf warbler favored low branches and vines for browsing and sturdy low branches for perching. It pumped its tail steadily, called spontaneously, and upon hearing playback of its own call moved in to investigate the source.
Without recording the call of the leaf warbler (call as well as song being a diagnostic separator of Sakhalin and Pale-legged), would I have been able to get an ID? Almost certainly not, said leaf-warbler expert Phil Round:
“I am a bit less sanguine on finding means (other than call frequency or song) to separate all [Pale-Saks]. Even in the hand, it is by no means clear. We can pick out long-winged male Sakhalin, and short-winged female Pale-legged. But there is more overlap than previously realized, and most are in between. There don’t appear to be any 100% consistent wing-formula differences, and plumage and bare-part features, while somewhat indicative, are again less than 100% reliable–especially under field conditions.” (Round, in litt., 2016; emphasis mine)
The most convenient separator of Pale-Sak is song, the cricket-like trill of Pale-legged being easily separable from the metallic whistle of Sakhalin. As Shanghai is not in the breeding range of either species, Pale-Sak songs are not often heard in Earth’s Greatest City. I have heard Sakhalin sing only once, on 5 May 2016 at Shanghai’s Zhongshan Park (Brelsford 2016). The song of Pale-legged I have heard at various locations in Shanghai as well as on its breeding grounds in Heilongjiang (Brelsford & Du 2017).
Although not as readily distinguishable as the songs, the “tink” calls of Pale-Sak differ markedly and consistently and are a reliable basis for an ID (Yap et al. 2014; Round et al. 2016; Weprincew et al. 1989). Yap et al. say the call of Pale-legged is of a “consistently higher frequency” than the call of Sakhalin. The calls that I have recorded of the two species show a difference in frequency of about 1 kHz, very much in line with others’ findings (Brelsford, August 2017; Brelsford, September 2017).
For birders unaccustomed to Pale-Sak calls, the difference may be hard to detect, especially at windy Cape Nanhui. A sound-recorder (which may be a smartphone) will pick up the difference, and an audio spectrogram will show it graphically. Solid, indisputable ticks, in some cases life ticks, await enterprising birders who sound-record.
In recent months, my work with sound-recordings has helped give Shanghai birders a clearer picture not only of Sakhalin Leaf Warbler but also of Kamchatka Leaf Warbler Phylloscopus examinandus, like Sakhalin a poorly known passage migrant through Shanghai (Brelsford, June 2017). In the case of Pale-Sak in Shanghai, a picture is emerging of overlapping migratory pathways. This finding comports with the findings of Yap et al. at Beidaihe, a thousand kilometers to the north. After analyzing calls obtained at Beidaihe of both Pale-legged and Sakhalin, Yap hypothesizes that in coastal Hebei “the migratory pathways of the two sister species may largely overlap” (2014).
How extensive is the Pale-Sak migratory overlap in Shanghai? How many of the Pale-Saks that we find in Shanghai each spring and autumn are Pale-legged, and how many are Sakhalin? Is there a peak passage time in Shanghai for each species, and if so, when is it?
Answers to these questions are currently unknown, but they are probably knowable, and it is very much possible for the citizen-scientists of Shanghai to be the producers of that knowledge. We only need to change our habits. When it comes to identifying lookalike species such as Pale-legged and Sakhalin Leaf Warbler, birders need to understand that photos do nothing to cut through the muddle. Only sound-recordings lead to indisputable records and a clearer picture of the species in Shanghai.
A clearer picture will add to our knowledge of the movement of leaf warblers along the central Chinese coast, focus attention on little-known East Asian species, and heighten the allure of Shanghai as a world-class birding location.
The sound-recordings and audio spectrograms below show clearly the difference in frequency between the calls of Sakhalin and Pale-legged Leaf Warbler.
Round, Philip D., Pierce, Andrew J., Saitoh, Takema, & Shigeta, Yoshimitsu. 2016. Addition of Kamchatka Leaf Warbler Phylloscopus examinandus and Sakhalin Leaf Warbler P. borealoides to Thailand’s Avifauna. Bulletin of the Japan Bird Banding Association 28: 9–21. Available here for download (708 KB) through shanghaibirding.com.
Weprincew, B. N., Leonowitsch, W. W. & Netschajew, W. A. 1989. Zur Lebensweise von Phylloscopus borealoides Portenko und Phylloscopus tenellipes Swinhoe. Mitteilungen aus dem Zoologischen Museum in Berlin 65 (Suppl.): 71–80. (German only)
Yap, F., Yong, D. L., Low, B., Cros, E., Foley, C., Lim, K. K. & Rheindt, F. E. 2014. First wintering record of the Sakhalin Leaf Warbler in South East Asia, with notes on vocalisations. BirdingASIA 21: 76–81. Downloadable here (accessed: 28 Sept. 2017).
Featured image: Sakhalin Leaf WarblerPhylloscopus borealoides, Cape Nanhui, Shanghai, 17 Sept. 2017. Craig Brelsford photographed and sound-recorded this individual, getting a rare record of the poorly known species in Earth’s Greatest City.
In the wake of my recent post on distinguishing Pale-legged Leaf Warbler from Sakhalin Leaf Warbler by call, I have been hoping to find more members of this species pair in Shanghai. On 4 Sept. 2017 at Pudong’s Cape Nanhui, my hopes were fulfilled in a big way. At the Magic Parking Lot (30.884889, 121.968222), not one but both species were calling.
Below, the recordings I made with my Olympus DM-650 pocket recorder. The first Sakhalin recording was made at Microforest 4 (30.953225, 121.959083), 7.7 km north of the Magic Parking Lot on the coastal road. The others were made at the Magic Parking Lot.
Note the higher frequency of the calls of Pale-legged–on average a full kilohertz higher. The difference is discernible by the keen listener, but nothing tells the story better than the spectrograms.
To summarize what I argued in the previous post: The calls, as well as the very distinctive songs, of Pale-legged Leaf Warbler and Sakhalin Leaf Warbler are diagnostic–that is, they differ markedly and consistently and are a reliable basis for an ID. The diagnosability of the calls of the two species has been affirmed by various researchers, among them Yap et al. (2014; Birding Asia 21: 76–81).
Featured image: Pale-legged/Sakhalin Leaf Warbler, Yangkou, Rudong, Jiangsu, 1 May 2014. Photo by Craig Brelsford. Some of the salient characteristics of Pale-Sak are pointed out. Separating Pale-legged from Sakhalin on the basis of plumage and bare parts is not possible; because this bird was neither singing nor calling, it cannot be determined to which of the two species it belongs.
Editor’s note: In the photo above, a Pale-legged Leaf Warbler emits its characteristic “tink” call in Microforest 4, Cape Nanhui, Pudong, 27 Aug. 2017. The tink call of Pale-legged is appreciably higher-pitched than that of Sakhalin Leaf Warbler. Distinguishing the two calls is the subject of this post. — Craig Brelsford
Last September, in “Pale-legged Leaf Warbler & the Shanghai Big 5,” I asserted that “Pale-legged Leaf Warbler is safely separable from Sakhalin Leaf Warbler only by song.” I was wrong. Call as well as song is a reliable separator. In this post, I am going to tell you how I arrived at this insight, and I will show you how you too can achieve clear, indisputable ticks of these tricky species through call alone.
Experts since at least as far back as 1989 have been arguing that Pale-legged Leaf WarblerPhylloscopus tenellipes and Sakhalin Leaf WarblerP. borealoides are separable not only by their distinctive songs but also by their calls. Thailand-based birder and shanghaibirding.com contributor Phil Round is among those making that argument. Round and his co-authors write: “[T]he call of P. tenellipes is markedly higher in frequency than that of P. borealoides” (Round et al., “Addition of Kamchatka Leaf Warbler Phylloscopus examinandus and Sakhalin Leaf Warbler P. borealoides to Thailand’s Avifauna,” downloadable through shanghaibirding.com).
If your ear is good, or even if your ear is just average and you have a sound-recorder, then you too can appreciate the higher frequency of the call of Pale-legged. A sound-recorder is very important, because if you upload your recordings to databases such as eBird and the Macaulay Library, then you will be able to “see” the sound in the audio spectrogram.
Now consider the spectrograms and sound-recordings of Pale-legged Leaf Warbler below. The spectrogram immediately below was recorded by me on 10 June 2016 in my wife Elaine Du’s hometown of Boli, Heilongjiang, part of the breeding range of Pale-legged Leaf Warbler. The call (here a grace note) and song both clock in at about 6 kHz, a frequency a full 25 percent higher than the call of Sakhalin Leaf Warbler and, as with Sakhalin, consistent with the frequencies of Pale-legged calls on xeno-canto.org.
The spectrogram below is of a brief sound-recording I made in Microforest 4 this past Sunday. The song element of this passage migrant is absent (though note that I have heard Pale-legged and Sakhalin singing in Shanghai in spring). The call has a frequency of 5.9 kHz and clearly belongs to Pale-legged Leaf Warbler.
Why should you care about all this? Because prepared birders have a chance to get solid ticks of “Pale-Saks” that are merely calling and not necessarily singing. If you hear a Pale-Sak calling and trust your ear (or better yet, sound-record the call and later analyze the spectrogram), then you may be able to go beyond the safe, boring record of “Pale-legged/Sakhalin Leaf Warbler” to a more satisfying full tick.
Accurate, plentiful records from Shanghai will help researchers such as Round get a clearer picture of the movements and population of these understudied species. As Round et al. write: “Increased sampling of migrants may also resolve the differences in timing of passage between P. examinandus and P. borealis on the one hand, and P. borealoides and P. tenellipes on the other” (“Addition”; hyperlink mine).
What’s more, you do not need to spend much or even know much to record good audio. My Olympus DM-650 costs less than US$250. I have no microphone other than the one built into my pocket recorder, I possess no parabola, and I use no editing software. My editing is limited to snipping off the unusable beginnings and endings of my sound-recordings, which I record in lossless 48kHz .wav. The very scientific-looking spectrograms displayed in this post are generated automatically by eBird and Macaulay.
In Shanghai in 2017, important facts about common birds such as Pale-legged Leaf Warbler and Sakhalin Leaf Warbler remain unknown. This ornithological semi-wilderness is both difficult and exciting. If we rise to the challenge and become better birders, then we will make new discoveries and blaze a trail of knowledge for future birders to follow.
* Audio spectrograms are available for every sound-recording on xeno-canto.org. On the unique page created for each recording, find the section “Actions” and click “Download full-length sonogram.”