Pale-legged Leaf Warbler making its high-pitched 'tink' call in Microforest 4, Cape Nanhui, Pudong, shanghai, China, 27 Aug. 2017. (Craig Brelsford)

Separating Pale-legged & Sakhalin Leaf Warbler on Call

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 Warbler Phylloscopus tenellipes and Sakhalin Leaf Warbler P. 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.

Our first exhibit is the spectrogram of a call I sound-recorded of Sakhalin Leaf Warbler on 8 May 2016 in Cape Nanhui’s Microforest 4 (30.953225, 121.959083). The frequency is 4.8 kilohertz, a number that matches closely the frequency of Sakhalin calls on xeno-canto.org.*

Audio spectrogram of call of Sakhalin Leaf Warbler.

Here is the sound-recording:

Sakhalin Leaf Warbler, call, Microforest 4 (30.953225, 121.959083), 8 May 2016 (00:15; 1 MB)

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.

Audio spectrogram of call plus song of Pale-legged Leaf Warbler.

Here is the sound-recording:

Pale-legged Leaf Warbler, call and song, Xidaquan National Forest (45.727751, 130.317316), Boli, Heilongjiang, 10 June 2016 (01:59; 6 MB)

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.

Audio spectrogram of call of Pale-legged Leaf Warbler.

The sound-recording:

Pale-legged Leaf Warbler, call, Microforest 4 (30.953225, 121.959083), 27 Aug. 2017 (00:01; 193 KB)

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.

Pale-legged Leaf Warbler Phylloscopus tenellipes pumping its tail vigorously while remaining otherwise motionless and while standing (as is its wont) on a thick branch (top panels); and a second individual making its high-pitched "tink" call (bottom panels). Microforest 4 (30.953225, 121.959083, top panels) and Microforest 1 (30.923889, 121.971635, bottom panels), Cape Nanhui, Pudong, Shanghai, China, 27 Aug. 2017.
Pale-legged Leaf Warbler Phylloscopus tenellipes performing typical behaviors. Top panels: pumping tail vigorously while remaining otherwise motionless on a sturdy branch. Bottom panels: making the high-pitched ‘tink’ call, again on a thick branch. Microforest 4 (30.953225, 121.959083, top panels) and Microforest 1 (30.923889, 121.971635, bottom panels), Cape Nanhui, 27 Aug. 2017. (Craig Brelsford)

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).

My trusty Olympus DM-650 sound recorder. In May, the height of migration season, my sound recorder is like the American Express card: 'Don't Leave Home Without It!'
My Olympus DM-650

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.”

Published by

Craig Brelsford

Craig Brelsford lived in Shanghai from 2007 to 2018. When he departed China, Craig was the top-ranked eBirder in the country, having noted 932 species, as well as the top-ranked eBirder in Shanghai (323 species). A 1993 graduate of the University of Florida, Craig was an award-winning newspaper editor in the United States for 10 years. In 2002, Craig earned a master's in business administration from the University of Liege in Belgium. Craig lives in Debary, Florida.

5 thoughts on “Separating Pale-legged & Sakhalin Leaf Warbler on Call”

  1. The diagnosability of the calls of Sakhalin and Pale-legged has already been examined and published in our paper (Yap et al. 2014; Birding Asia 21: 76–81). You should probably mention this somewhere.

    1. Thanks for reading, congratulations on your paper, and thanks for calling our attention to it; the more resources, the better.

      You understand, I’m sure, that I wrote a post, not a scholarly article, and that I made no attempt to treat exhaustively, nor did I perceive an obligation on my part to treat exhaustively, the papers published on the subject of Pale-Sak calls.

      As I give preference to the work of contributors to shanghaibirding.com, and inasmuch as Phil Round has written a guest post for and made other notable contributions to this site, I felt a particularly strong need to refer to his work in my post.

      Others’ work on Pale-Sak may be just as deserving of mention as the article I cited; I don’t pretend to have the last word on the subject. I therefore welcome the information you have provided.

  2. Dear Craig,

    Your post on separating Pale-legged and Sakhalin Leaf Warbler on call was very interesting for the editors of Dutch Birding (https://www.dutchbirding.nl/journal), particularly in context of the vagrancy of both species to the Western Palearctic (the first record of Pale-legged in the WP was last autumn).

    Maybe you are interested in adapting your text from blog for a short paper to Dutch Birding? It would be very useful for WP birders in looking for both species during autumn migrantion/vagrancy of the eastern Phylloscopus species in the WP.

    All the best
    Lukasz Lawicki
    Dutch Birding

    1. Hi Lukasz,

      I will be honored to write for Dutch Birding. I feel a particularly strong connection to Dutch Birding, because I lived in the Netherlands from 2001 to 2007 and began my birding career there.

  3. Good article. In Thailand last winter I found the difference in calls quite noticeable. I also thought that I had some birds calling in the tops of trees on the summit of Doi Lang. These sounded like Sakhalin. All the Pale-legged I saw were in scrub, low down.

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