Kamchatka Leaf Warbler in Shanghai

by Craig Brelsford
Founder, shanghaibirding.com

Seen at Pudong’s Cape Nanhui on 4 June: Kamchatka Leaf Warbler Phylloscopus examinandus. Veteran British birder Michael Grunwell and I found our 4 Kamchatkas in Microforest 4 (30.953225, 121.959083), the largest of the tree plantations on the landward side of the sea wall. The species is an all-time first for the Shanghai eBird list.

Just after sunrise, Michael and I, as is our wont, were doing “drive-by birding”—creeping along the edge of the road, listening out for birds. Suddenly, I heard an unfamiliar sound.

My gut said, “Hard, loudTaiga Flycatcher?”

Taiga was not even close, of course. Note, however, what my gut was not saying: “Arctic Warbler,” a bird whose call I know well. This call was decidedly not an Arctic’s, though it soon dawned on us that we were hearing some type of leaf warbler.

To see why my gut did not say Arctic, compare my recordings of the tight “tzit” call of Arctic Warbler with the looser call of Kamchatka Leaf Warbler:

Arctic Warbler Phylloscopus borealis, Jiangsu (32.560095, 121.041956), May (00:09; 1.9 MB)

Kamchatka Leaf Warbler P. examinandus, Microforest 4 (30.953225, 121.959083), Cape Nanhui, 4 June (00:25; 4.9 MB)

Michael and I skidded to a stop and poked our heads into the green tangle of locust trees. The call was being followed by a song. Only upon hearing the song did I think of Arctic Warbler. But here too, the song, though similar, was distinctive—wavier than the straight trill of Arctic. Look at the spectrograms below.

Spectrogram

The spectrogram above is of my recording 4 June of Kamchatka Leaf Warbler. Note the pattern: downward sweeps followed by an upward sweep. No one would liken that song to an insect’s. Below, the spectrogram of my recording of the song of Arctic Warbler. Note the straight, cricket-like trill.

Spectrogram

Here are the recordings whose spectrograms are shown above:

Arctic Warbler, Yikesama National Forest, Inner Mongolia (52.150833, 121.465639), July (01:00; 3.2 MB)

Kamchatka Leaf Warbler, Microforest 4, 4 June (00:48; 9.3 MB)

After hearing several song-call cycles, Michael, my more experienced partner, first said the words “Kamchatka Leaf Warbler.”

Michael has birded the Indonesian islands of Flores and Komodo, where Kamchatka Leaf Warbler winters. Michael said that, last winter, walking through the forests there, he heard dozens of times the call of P. examinandus.

“I know that call,” Michael said.

I whipped out my Olympus DM-650 voice recorder and recorded the calling and singing warbler. Meanwhile, we caught our first glimpse of the individual. It was clearly an “Arctic-type” leaf warbler.

What is an “Arctic-type” leaf warbler? An Arctic-type leaf warbler is a member of one of four closely related taxa divided among three species: Japanese Leaf Warbler Phylloscopus xanthodryas, Kamchatka Leaf Warbler P. examinandus, and Arctic Warbler P. borealis borealis and P. b. kennicotti.

map
Leaf-warbler expert and Shanghai Birding member Per Alström is the person most responsible for our current understanding of Arctic-type leaf warblers. Alström’s PDF, from which this page is taken, is a handy introduction to leaf warblers in China and is downloadable through shanghaibirding.com.

Arctic Warbler is by far the most widespread breeder in the complex. P. b. borealis breeds across northern Eurasia, from Scandinavia to northeast China and the Russian Far East. P. b. kennicotti breeds in western Alaska.

As their names suggest, Japanese Leaf Warbler breeds mainly in Japan (Honshu, Shikoku, Kyushu), Kamchatka Leaf Warbler mainly in the southern Kamchatka Peninsula (as well as on Hokkaido and Sakhalin and in the Kuril Islands).

In 2010 Shanghai Birding member Per Alström et al. proposed the current way of viewing the Arctic-type warblers. Previously, the taxon examinandus was putative, not even reaching the subspecies level; Alström and his team showed that examinandus, with its distinctive song and call, merits recognition not as a subspecies of Arctic Warbler but as a species in its own right.

Of the three Arctic-type species, Japanese Leaf Warbler most stands out, being on average yellower than the two others. Arctic and Kamchatka look much more alike.

There are, however, some slight differences. Kamchatka is said to have a “marginally longer bill, tarsi and tail” than Arctic (del Hoyo & Collar). Sure enough, the Kamchatka I photographed is long-billed. Take a look below.

warblers
Arctic Warbler (top) and Kamchatka Leaf Warbler. Both birds show the classic features of Arctic-type warblers, among them a long supercilium that does not reach bill base, a dark smudge on the lower mandible, and mottled ear coverts. Kamchatka is said to be slightly greener on average than Arctic, a description that these photos do not contradict. The bill of Kamchatka is also marginally longer than Arctic’s, and in these profile shots one notes the longer bill of the Kamchatka and the stouter bill of the Arctic. I would not suggest basing an Arctic-Kamchatka ID on plumage and bare parts. Plumage and bare parts can, however, enhance the quality of a song- or call-based ID. Top: South Lock (30.860073, 121.909997), Cape Nanhui, 13 May. Bottom: Microforest 4 (30.953225, 121.959083), 4 June. (Craig Brelsford)

Michael and I heard our loudest song and calls during that first, early morning encounter. However, we heard Kamchatka calling throughout the day.

Our new Shanghai record, combined with late-May and early-June records from nearby Zhejiang, suggests that in this region, once the wave of Arctics passes through around 15 May, Kamchatka Leaf Warbler may be the Arctic-type to look out for.

BIBLIOGRAPHY

Alström P., T. Saitoh, D. Williams, I. Nishiumi, Y. Shigeta, K. Ueda, M. Irestedt, M. Björklund & U. Olsson (2011). The Arctic Warbler Phylloscopus borealis—three anciently separated cryptic species revealed. Ibis 153:395-410. Available at https://www.shanghaibirding.com/wp-content/uploads/2019/04/Alstrom-et-al-2011-Arctic-Warblers-IBIS.pdf (accessed 5 Aug 2020).

Brelsford, C. (2017). eBird Checklist: https://ebird.org/ebird/view/checklist/S37369822. eBird: An online database of bird distribution and abundance [web application]. eBird, Ithaca, New York, USA (accessed 22 Apr 2020).

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Brelsford, Craig, moderator. Shanghai Birding, a WeChat group. Discussions with various birders, chief among them Hangzhou birder Cheng Qian, who had information about sightings of P. examinandus in Zhejiang. Beijing-based Swedish birder Jan-Erik Nilsén also provided timely advice. To join Shanghai Birding, in WeChat, friend Craig Brelsford (WeChat ID: craigbrelsford). In your friend request, please make it clear that you wish to join Shanghai Birding.

del Hoyo, J. & Collar, N. (2017). Kamchatka Leaf-warbler (Phylloscopus examinandus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona, Spain (retrieved from https://www.hbw.com/node/1343935 on 22 Apr 2020).

Jackett, N. (25 Feb. 2016). First Kamchatka Leaf Warbler recorded for Australian Mainland. eBird Australia: https://ebird.org/content/australia/news/first-recorded-kamchatka-leaf-warbler-for-australian-mainland/. eBird, Ithaca, New York, USA. ebird.org (accessed 22 Apr 2020).

Featured image: Kamchatka Leaf Warbler Phylloscopus examinandus. At Shanghai’s Cape Nanhui, birders Michael Grunwell and Craig Brelsford found the individual pictured here and three others. (Craig Brelsford)
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Comparing Blyth’s Pipit & Richard’s Pipit

by Craig Brelsford
Founder, shanghaibirding.com

With more and more birders operating in Shanghai, more and more vagrant birds are bound to be discovered. One possibility is Blyth’s Pipit Anthus godlewskii (photo above, L), a species similar to our familiar Richard’s Pipit A. richardi (R). Blyth’s breeds mainly in Mongolia, occurs on passage in central China, and winters mainly in India, so any records here would be of extralimitals. Let’s examine here how to separate the two pipits.

Comparison of pipits
Comparison of adult-type Richard’s Pipit Anthus richardisinensis‘ (1) and adult Blyth’s Pipit A. godlewskii (4). The population group A. r. ‘sinensis’ occurs in southeast China south of the Yangtze River. Structurally, ‘sinensis‘ is the smallest group in Richard’s, with proportions recalling Blyth’s. Note however the blackish centers to the median coverts (2, 3). In adult-type Richard’s (2), the centers are triangular and tinged rufous at the edges. In adult Blyth’s (3), the centers are squarish, less rufous-tinged, and more clear-cut. 1, 2: Cape Nanhui, December. 3, 4: Hulunbeier, Inner Mongolia, July. (Craig Brelsford)

The key to getting a Blyth’s in Shanghai is paying attention to the many Richard’s Pipit that we see in the area. Anthus richardi is more or less a passage migrant in the Shanghai area and is recorded here regularly in spring and autumn. Some are present in winter; Elaine Du and I had a “sinensis” last week, the ID’ing of which led to this post.

flight song
More views of Blyth’s Pipit performing flight song, Inner Mongolia, July. In Pipits and Wagtails, Shanghai Birding member Per Alström et al. write that in flight, Blyth’s Pipit ‘often recalls one of the smaller pipits rather than Richard’s’ (237). Note however that Anthus richardi ‘sinensis,’ a population group within Richard’s Pipit often found in Shanghai, is structurally similar to Blyth’s. (Craig Brelsford)

Richard’s “sinensis” is very similar to Blyth’s, being best told by song, which is rarely heard in the Shanghai area. According to Per Alström et al., whose book Pipits and Wagtails is the authority on Palearctic and Nearctic pipits, the song of Blyth’s is “very characteristic and completely different from [that] of Richard’s” (242). During a trip in July 2015 to the Inner Mongolian prefecture of Hulunbeier, one of the few places in China where Blyth’s breeds, I recorded the song.

Blyth’s Pipit, flight song, recorded 22 July 2015 at a point (48.767866, 116.834183) near Hulun Lake, Inner Mongolia (2.1 MB; 00:32)

The calls of the two species also differ, but less markedly. The flight call of Richard’s is a common bird sound in Shanghai during migration season. The call of Blyth’s is similar enough to “cause problems even for some veteran observers” (Alström et al. 244). For Shanghai birders, even those unfamiliar with Blyth’s, a “Richard’s” with a strange flight call is worth your attention. Listen for what Alström et al. describe as a call “less harsh, softer and more nasal” than Richard’s (244). For reference, review the flight call of Richard’s:

Richard’s Pipit, flight call, Dishui Lake, Shanghai, February (00:01; 852 KB)

Regarding plumage, the most reliable differentiator of Richard’s and Blyth’s is the pattern of the median coverts. In Blyth’s, a typical adult-type median covert will show well-defined, squarish black centers. In Richard’s, the adult-type median coverts are less clear-cut, rufous-tinged, and triangular. Note that the fresher the plumage, the more reliable this differentiator is.

Another less reliable criterion is structure. Shanghai birders will agree that the first impression a non-“sinensis” Richard’s usually gives is “large pipit.” Other pipits, such as Buff-bellied Pipit, Red-throated Pipit, and Olive-backed Pipit, give a “small pipit” impression.

Richard's Pipit
Richard’s Pipit, Jiangsu, September. Alström et al. urge care in ID’ing Blyth’s and Richard’s. Here, the median coverts of this Richard’s appear squarish, like Blyth’s (bottom R, inset). But note the date of the photo: September, a time of year when most Richard’s show worn plumage. ‘In worn plumage,’ the authors write, ‘the shape of the dark centres to the secondary coverts is generally less obviously different, and the pale tips can be much the same colour in both species’ (237). The ID of this Richard’s was derived from its call, a more constant characteristic, and not from the appearance of its median coverts, a more variable characteristic. (Craig Brelsford)

Alström et al. say, and I having seen Blyth’s can concur, that a birder viewing Blyth’s will get a “small pipit” impression: “The smaller size, lighter build and shorter tail,” the authors write, “are often most apparent in flight, when [Blyth’s] often recalls one of the smaller pipits rather than Richard’s.” Note also that the smaller size and shorter bill, tail, and hind claw of Blyth’s give that species a “better proportioned” look than the larger and heavier Richard’s (237).

The directions above should be seen as guidelines; individual Richard’s and Blyth’s may defy easy categorization, “sinensis” Richard’s even more so. Alström et al. caution against jumping the gun with your ID: “It is crucial to realise that in both species (especially Richard’s) appearance can vary considerably in one and the same individual depending on mood, weather, etc.,” they write. “Also, some Richard’s are structurally very like Blyth’s; this is especially true of southern Chinese Richard’s (‘sinensis’)” (237).

A record of Blyth’s Pipit in Shanghai would shoot to the top of the “Year’s Best” list. The stakes are high, so look diligently, and use caution. Good luck!

BIBLIOGRAPHY

Alström, Per, Krister Mild & Bill Zetterström. Pipits and Wagtails. Princeton University Press, 2003. This landmark book, co-authored by Shanghai Birding member Per Alström, is my first reference on all things Motacillidae.

Brazil, Mark. Birds of East Asia. Princeton University Press, 2009. Serviceable descriptions of Blyth’s Pipit and Richard’s Pipit. Illustration of “sinensis.”

Svensson, Lars & Killian Mullarney & Dan Zetterström. Collins Bird Guide, 2nd ed. HarperCollins, 1999-2009. Outstanding illustrations of Richard’s Pipit and Blyth’s Pipit by Mullarney.
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Pale-legged Leaf Warbler & the Shanghai Big 5

The illustration above shows Shanghai’s Big 5 Leaf Warblers: Pale-legged Leaf Warbler (1), Arctic Warbler (2), Eastern Crowned Warbler (3), Pallas’s Leaf Warbler (4), and Yellow-browed Warbler (5). In this post, I tell you how to separate Pale-legged and its lookalike Sakhalin Leaf Warbler from the others.

by Craig Brelsford
Founder, shanghaibirding.com

Recently at Cape Nanhui, the birding hotspot in Pudong, my object of observation was Pale-legged Leaf Warbler, one of the Big 5 Leaf Warblers in Shanghai. In both spring and autumn, Phylloscopus tenellipes passes through Earth’s Greatest City in considerable numbers. A lookalike species, Sakhalin Leaf Warbler P. borealoides, also passes through Shanghai.

In this post, I shall outline the difficulty of distinguishing Pale-legged Leaf Warbler from Sakhalin Leaf Warbler on anything but call and song, and I will show you some of the traits of “PaleSak” that set this species pair apart from other leaf warblers.

SONG CAN SAFELY SEPARATE PALE-LEGGED FROM SAKHALIN

Per's PDF
‘Almost identical’: that’s the judgment of leaf-warbler expert Per Alström on Pale-legged Leaf Warbler and Sakhalin Leaf Warbler (regarding their plumage and bare parts). The page shown here is No. 11 of a 40-page PDF on leaf warblers in China by Professor Alström. The PDF is a handy introduction to a difficult group and can be downloaded here (13 MB).

Pale-legged Leaf Warbler is safely separable from Sakhalin Leaf Warbler only by song and call. Every other trait of each can occur in the other. Numerous authorities confirm this. Swedish ornithologist Per Alström calls the two species “almost identical” and “virtually indistinguishable except by song” (Alström 2012). Mark Brazil says field separation of PaleSak is “uncertain,” and he warns readers to “beware light conditions” (2009). Clement writes that Pale-legged and Sakhalin are “very similar” and claims, dubiously, that the latter is distinguishable from the former “mainly by greener upperparts and lack of wingbars” (2006). Clements goes on to describe juvenile Pale-legged as being “more greenish on upperparts,” which begs the question of whether the greenish PaleSak one is observing is an adult Sakhalin or a juvenile Pale-legged. Moreover, a quick look at Oriental Bird Images shows many Sakhalin Leaf Warbler with wing bars.

Thankfully for us birders, the songs of the two species are distinctive and provide the basis for a safe ID. The song of Pale-legged, occasionally heard in Shanghai in May, is a cricket-like trill, that of Sakhalin a high-pitched, three-note whistle.

Pale-legged Leaf Warbler, Heilongjiang, China, June (02:00, 6.4 MB; Craig Brelsford)

Sakhalin Leaf Warbler, Zhongshan Park, Shanghai, May (00:36; 2.2 MB; Craig Brelsford)

One day in May, I heard Pale-legged and Sakhalin singing together in Zhongshan Park—proof that Sakhalin passes through Shanghai. Usually, however, birders here are forced to perform the less than satisfying task of assigning the individuals they see to the category “Pale-legged/Sakhalin Leaf Warbler.”

Bottom line: In Shanghai, any PaleSak one sees is probably Pale-legged Leaf Warbler, the continental breeder, and not Sakhalin Leaf Warbler, the breeder from the eponymous Russian island plus Hokkaido and Honshu; but to claim certainty about any non-singing individual is the taxonomical version of Russian roulette.

DISTINGUISHING PALESAK FROM OTHER LEAF WARBLERS

The PaleSak species pair is readily distinguishable from other leaf warblers, in particular the other four members of Shanghai’s Big 5: Pallas’s Leaf Warbler Phylloscopus proregulus, Yellow-browed Warbler P. inornatus, Arctic Warbler P. borealis, and Eastern Crowned Warbler P. coronatus.

Here are a few principles:

Pale-legged Leaf Warbler and Sakhalin Leaf Warbler are plain, mid-sized to large leaf warblers without even the hint of a coronal stripe.

Pale-legged/Sakhalin
Pale-legged/Sakhalin Leaf Warbler shows no trace of a crown stripe (Panel 1). Yellow-browed Warbler (2) usually shows a faint stripe. In Eastern Crowned Warbler (3) and Pallas’s Leaf Warbler (4), the stripe is prominent. (Craig Brelsford)

Pale-legged/Sakhalin Leaf Warbler has distinctive pink legs and a short bill with a black smudge on the lower mandible, which is pink at the base and tip.

warblers
Like Pale-legged/Sakhalin Leaf Warbler, species in the Arctic Warbler Complex lack a crown stripe and usually show one or two wing bars. One way to distinguish birds from the two groups is by the color of the legs and bill. The legs (Panel 1) of Pale-legged/Sakhalin Leaf Warbler are distinctively pale and pink, in contrast to the brownish-yellow legs of the Arctic-type Warbler in 2. Likewise, the slightly shorter bill of Pale-legged/Sakhalin (3) shows a blackish upper mandible and pinkish lower mandible and cutting edge. The black smudge on the lower mandible does not reach the tip. The bill of Arctic-type Warbler (4) follows a similar pattern, but with brownish-yellow replacing pink. (Craig Brelsford)

Even on a fast-moving PaleSak in poor light, the pink of the bill and especially of the legs is readily seen. The distinctive pale color of these bare parts is a handy tool for distinguishing PaleSak from birds in the Arctic Warbler Complex, which like PaleSak lack a crown stripe and usually show one or two wing bars. (The Arctic Warbler Complex consists of Arctic Warbler Phylloscopus borealis, Kamchatka Leaf Warbler P. examinandus, and Japanese Leaf Warbler P. xanthodryas. In Shanghai, Arctic Warbler is the most common of the three, migrating through Shanghai every spring and autumn.) The pink coloration also distinguishes PaleSak from Dusky Warbler P. fuscatus, an uncommon migrant and winter visitor in Shanghai, and the scarce passage migrant Two-barred Warbler P. plumbeitarsus.

Pale-legged/Sakhalin Leaf Warbler constantly pumps its tail.

tail
The tail of Pale-legged/Sakhalin Leaf Warbler pumps independently of other muscular actions. In panels 1-2, note that the tail pumps even as the warbler devours an insect. Panels 3-4 show the warbler motionless except for the up-and-down movement of the tail. Photos here and immediately below are of a single individual and were taken in September at Microforest 4 (30.953225, 121.959083), Cape Nanhui, Shanghai. (Craig Brelsford)

The tail-pumping of Pale-legged/Sakhalin is one of the most distinctive behavioral traits of the species pair. The steady movement usually occurs independently of other muscular actions and is slow enough for the eye to see. The tail-flicking of Arctic Warbler, by contrast, is more spasmodic and is often accompanied by wing-flicking.

Pale-legged/Sakhalin Leaf Warbler is often found on the lower, thicker branches of trees.

Pale-legged/Sakhalin Leaf Warbler
Pale-legged/Sakhalin Leaf Warbler on thick branch. More so than other leaf warblers, PaleSak is likely to be seen on leafless, thick branches low on the tree. (Craig Brelsford)

With its ability to forage along thick branches and not just glean from the underside of leaves, Pale-legged/Sakhalin can remind one of a nuthatch. Other species such as Arctic Warbler use the lower branches, but sustained observation shows PaleSak more often in those areas. Note: In May and June 2016, I studied Pale-legged Leaf Warbler on its breeding grounds in Heilongjiang. There, amid trees older and taller than one usually sees in Shanghai, I most often noted the species far above my head, in the mid-canopy.

A NOTE ON CALLS

Except for the mainly silent migrant Eastern Crowned Warbler, Shanghai’s Big 5 Leaf Warblers all call in both spring and autumn. The calls are distinctive. The metallic “tink” of PaleSak contrasts markedly with the “tzit” of Arctic Warbler, the “dweet” of Pallas’s Leaf Warbler, and the “sweet” of Yellow-browed Warbler.

Sakhalin Leaf Warbler, Cape Nanhui, Shanghai, May (00:15; 1.4 MB)

Arctic Warbler, Jiangsu, May (00:09; 1.9 MB)

Pallas’s Leaf Warbler, Jiangsu, May (00:05; 1.6 MB)

Yellow-browed Warbler, Lesser Yangshan Island, Zhejiang, April (00:07; 1.7 MB)

UPDATE

Editor’s note: This post caught the attention of Philip D. Round, a professor at Mahidol University in Bangkok and an expert on leaf warblers. In an e-mail to me, Round writes that as discoveries are made and papers published, separating Pale-legged Leaf Warbler from Sakhalin Leaf Warbler on call may become more widespread. Separation on morphology, by contrast, will be much more difficult, though it may eventually turn out to be possible in the hand.

The following paragraphs are from Round’s e-mail to me:

“I enclose a paper that details the first records of both Kamchatka Leaf Warbler and Sakhalin Leaf Warbler from Thailand. [Editor’s note: the paper, “Addition of Kamchatka Leaf Warbler Phylloscopus examinandus and Sakhalin Leaf Warbler P. borealoides to Thailand’s Avifauna,” is available for download through shanghaibirding.com (708 KB).] This has been rather overtaken by events, as we have now caught into the hundreds of Sakhalin LW, mostly on spring passage, and quite a few more Kamchatka. I have an undergraduate student who has carried out DNA assay on about ten percent of all the Pale-legged and Sakhalin LW caught. For many of these we have also recorded call notes on release. When she comes back from overseas study in January 2017 I hope we’ll get a paper out which publishes details of call-note frequency and DNA results for this large sample, which should show the correlation between species and call-note frequency clearly. (Actually this is moderately and anecdotally well-known already. I think either Frank Lambert or Jonathan Martinez was the first to draw my attention to the difference, and it is mentioned by Yap et al. in BirdingASIA with reference to an overwintering Singapore bird.) [Note: Round is referring to Yap, Francis et al., “First wintering record of the Sakhalin Leaf Warbler Phylloscopus borealoides in South-East Asia, with notes on vocalisations,” BirdingASIA 21 (2014): 76–81.]

“I am a bit less sanguine on finding means (other than by call frequency or song) to separate all birds. 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. But probably we are missing something. The next thing to do is to apply PCA or some other multivariate analysis to figure out reliable means of separation of birds in the hand from our large sample, and also to use the information we have to figure out differences in the timing of passage of the two spp.”

BIBLIOGRAPHY

Alström, P. (2012). Identification of Phylloscopus & Seicercus Warblers in China. Notes from presentation given to Beijing Birdwatching Society in November 2012. PDF downloadable here (13 MB). Click here for a 5 MB zip archive containing all 40 pages of the report in JPEG form. Those pages can be synced to your smartphone like photographs and consulted in the field. (Accessed: 5 Aug 2020)

Brazil, M. (2009). Birds of East Asia. Princeton, New Jersey: Princeton University Press.

Clement, P. (2006). Family Sylviidae (Old World Warblers). Pp. 663-4 (Pale-legged Leaf Warbler, Sakhalin Leaf Warbler) in del Hoyo, J., Elliott, A. & Christie, D.A. eds. (2006). Handbook of the Birds of the World. Vol. 11. Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona, Spain.

Featured image: Shanghai’s Big 5 leaf warblers. (Craig Brelsford)
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