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).

Pale-legged Leaf Warbler & the Shanghai Big 5

Editor’s note: 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.

Last Sat. 24 Sept. 2016 at Nanhui, my object of observation was Pale-legged Leaf Warbler, one of the Big 5 Leaf Warblers in the Shanghai region. In both spring and autumn, Phylloscopus tenellipes passes through Earth’s greatest city in considerable numbers, giving Shanghai birders ample opportunity to study it. A lookalike species, Sakhalin Leaf Warbler P. borealoides, also has been noted in Shanghai.

In this post, I shall outline the near-impossibility of distinguishing Pale-legged Leaf Warbler from Sakhalin Leaf Warbler on anything but song, and I will show you some of the traits of “Pale-Sak” that set this species pair apart from other leaf warblers. I also have a roundup of the other birds I noted this past Saturday.

ONLY SONG CAN SAFELY SEPARATE PALE-LEGGED FROM SAKHALIN

Per's PDF, page 11
‘Almost identical’: that’s the judgment of leaf-warbler expert Per Alström on Pale-legged and Sakhalin Leaf Warbler. The page shown here is No. 11 of a 40-page PDF on leaf warblers in China that Professor Alström wrote in 2012. 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. 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” (1). Mark Brazil says field separation of Pale-Sak is “uncertain,” and he warns readers to “beware light conditions” (2). P. 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” (3). Clements goes on to describe juvenile Pale-legged as being “more greenish on upperparts,” which begs the question of whether the greenish Pale-Sak 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, Boli County, Heilongjiang, 10 June 2016 (02:00, 6.4 MB)

Sakhalin Leaf Warbler, Zhongshan Park, Shanghai, 5 May 2016 (00:36; 2.2 MB)

One day last 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 Pale-Sak 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 PALE-SAK FROM OTHER LEAF WARBLERS

The Pale-Sak 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 has no crown stripe.
Pale-legged/Sakhalin Leaf Warbler shows no trace of a crown stripe (Panel 1). Yellow-browed Warbler usually shows a faint stripe (2). 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.

Bill and legs of Pale-legged Leaf Warbler compared to those of Arctic Leaf Warbler.
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 Pale-Sak 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 Pale-Sak from birds in the Arctic Warbler Complex, which like Pale-Sak 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 Pale-Sak 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.

The tail of Pale-legged/Sakhalin Leaf Warbler pumps independently of other muscular actions.
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 at Microforest 4 (30.953225, 121.959083), Nanhui, 24 Sept. 2016. (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 on thick branch.
Pale-legged/Sakhalin Leaf Warbler on thick branch. More so than other leaf warblers, Pale-Sak is likely to be seen on leafless, thick branches low on the tree.

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 Pale-Sak 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 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 Pale-Sak contrasts markedly with the “tzit” of Arctic Warbler, the “dweet” of Pallas’s Leaf Warbler, and the “sweet” of Yellow-browed Warbler.

Pale-legged/Sakhalin Leaf Warbler, Nanhui, Shanghai, 8 May 2016 (00:15; 1.4 MB)

Arctic Warbler, Yangkou, Rudong, Jiangsu, 16 May 2015 (00:09; 1.9 MB)

Pallas’s Leaf Warbler, Yangkou, Rudong, Jiangsu, 9 May 2014 (00:05; 1.6 MB)

Yellow-browed Warbler, Lesser Yangshan Island, Zhejiang, 24 April 2014 (00:07; 1.7 MB)

Note that, according to Brazil, the call of Pale-Sak only can separate the pair from other species. It cannot be used to separate Pale-legged from Sakhalin. The tink of Pale-legged, Brazil writes, “is probably indistinguishable from Sakhalin Leaf” (2).

UPDATE: 19 OCT. 2016

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 written 18 Oct. 2016, 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.”

ROUNDUP FOR SATURDAY 24 SEPT. 2016

Stimulating discussions about leaf warblers enlivened the lulls on a day in which my wife Elaine Du and I once again partnered with veteran British birder Michael Grunwell. We noted 69 species, starting at the sod farm south of Pudong airport then spending the rest of the day at Nanhui. We reunited briefly with the Sino-German birding duo of Xueping and Stephan Popp, and we met Dutch birder Benjamin Muis. Highlights:

Ruff

Ruff, by Elaine Du.
Note the scaly upperparts and buffy head of this juvenile Ruff, as well as the white sides to its tail. Elaine got these shots with my iPhone 6 plus Swarovski ATX-95 spotting scope mounted atop our Manfrotto head and Gitzo tripod.

Juvenile spotted on mudflats at high tide. A far-northern, trans-Eurasian breeder, Philomachus pugnax is a scarce passage migrant in Shanghai. Amid the greenshanks and godwits, the Ruff stood out with its buff-washed head and scaly upperparts. Juvenile Ruff resembles Buff-breasted Sandpiper, a much smaller American bird that we quickly ruled out.

Eurasian Hobby

Peregrine Falcon, Nanhui, 24 Sept. 2016.
Eurasian Hobby, Nanhui, 24 Sept. 2016.

1 juv. Earlier mis’ID as Peregrine Falcon; corrected 3 Oct. 2016. Thanks to the commenters below for pointing out the error.

White-winged Tern

A week ago ca. 2500, on Saturday only 10. Coastal birding is a parade of change, especially in migration season.

Other goodies: Eurasian Wryneck 2, Japanese Paradise Flycatcher 6, Amur Paradise Flycatcher 1, Richard’s Pipit 5, White’s Thrush 5 first-of-season, Rufous-tailed Robin 1 first-of-season. We introduced Benjamin to Reed Parrotbill calling unseen from the reeds below, we had a strong count of 16 Blue-and-white Flycatcher, and we noted two endangered species: Far Eastern Curlew and Yellow-breasted Bunting.

Day Lists
My first reference is IOC World Bird List.

List 1 of 2 for Sat. 24 Sept. 2016 (10 species). Birds noted at sod farm south of Pudong International Airport (31.112586, 121.824742), Pudong, Shanghai, China. Sunny. Low 18° C, high 26° C. Humidity 71%. Visibility 10 km. Wind ESE 11 km/h. PM2.5 AQI: 98 (moderate). Sunrise 05:44, sunset 17:46. SAT 24 SEP 2016 06:05-06:20. Craig Brelsford, Elaine Du, & Michael Grunwell.

Little Egret Egretta garzetta 2
Eastern Cattle Egret Bubulcus coromandus 3
Little Ringed Plover Charadrius dubius 50
Common Snipe Gallinago gallinago 3
Wood Sandpiper Tringa glareola 1
Spotted Dove Streptopelia chinensis 2
Long-tailed Shrike Lanius schach 2
Eastern Yellow Wagtail Motacilla tschutschensis tschutschensis ca. 50
White Wagtail M. alba leucopsis 6
Richard’s Pipit Anthus richardi 4

List 2 of 2 for Sat. 24 Sept. 2016 (66 species)

Microforest 4
Microforest 4 (30.953225, 121.959083), Saturday. This is the largest of the eight microforests at Nanhui and an astonishingly effective migrant trap. With woodland birds migrating through and trees all around, one almost begins to forget that this speck of woodland is just a stone’s throw from the mudflats and the East China Sea. German birder Kai Pflug recently carted out trash from the wood, enhancing its allure. (Craig Brelsford)

Birds noted around Pudong Nanhui Dongtan Wetland (Pǔdōng Nánhuì Dōngtān Shīdì [浦东南汇东滩湿地]; 30.920507, 121.973159), Pudong, Shanghai, China. Includes birds found along coastal road between 31.000204, 121.938145 & 30.851114, 121.848527, in particular Microforest 4 (30.953225, 121.959083). Sunny. Low 18° C, high 26° C. Humidity 71%. Visibility 10 km. Wind ESE 11 km/h. PM2.5 AQI: 98 (moderate). Sunrise 05:44, sunset 17:46. SAT 24 SEP 2016 06:40-17:35. Craig Brelsford, Elaine Du, & Michael Grunwell.

Eurasian Wigeon Anas penelope 5
Eurasian Teal A. crecca ca. 300
Common Pheasant Phasianus colchicus 5
Little Grebe Tachybaptus ruficollis 40
Great Crested Grebe Podiceps cristatus 1
Yellow Bittern Ixobrychus sinensis 1
Grey Heron Ardea cinerea 30
Great Egret A. alba 13
Intermediate Egret A. intermedia 2
Little Egret Egretta garzetta 12
Eastern Cattle Egret Bubulcus coromandus 20
Chinese Pond Heron Ardeola bacchus 4
Black-crowned Night Heron Nycticorax nycticorax 10
Common Moorhen Gallinula chloropus 2
Eurasian Coot Fulica atra 8
Black-winged Stilt Himantopus himantopus 5
Pied Avocet Recurvirostra avosetta 5
Grey Plover Pluvialis squatarola 1
Kentish Plover Charadrius alexandrinus 100
Far Eastern Curlew Numenius madagascariensis 1
Black-tailed Godwit Limosa limosa melanuroides 14
Red-necked Stint Calidris ruficollis 20
Dunlin C. alpina 30
Green Sandpiper Tringa ochropus 4
Spotted Redshank T. erythropus 4
Common Greenshank T. nebularia 30
Marsh Sandpiper T. stagnatilis 8
Common Redshank T. totanus 5
Ruff Philomachus pugnax 1
White-winged Tern Chlidonias leucopterus 10
Whiskered Tern C. hybrida 5
Feral Pigeon (Rock Dove) Columba livia 5
Spotted Dove Streptopelia chinensis 6
Cuculus sp. 4
Common Kingfisher Alcedo atthis 1
Eurasian Wryneck Jynx torquilla 2
Eurasian Hobby Falco subbuteo 1 juv.
Black-winged Cuckooshrike Coracina melaschistos 1
Brown Shrike Lanius cristatus 3
Long-tailed Shrike L. schach 28
Black-naped Oriole Oriolus chinensis 1
Black Drongo Dicrurus macrocercus 1
Japanese Paradise Flycatcher Terpsiphone atrocaudata 6
Amur Paradise Flycatcher T. incei 1
Oriental Skylark Alauda gulgula 3
Sand/Pale Martin Riparia riparia/diluta 1
Barn Swallow Hirundo rustica ca. 200
Light-vented Bulbul Pycnonotus sinensis 4
Yellow-browed Warbler Phylloscopus inornatus 1
Pale-legged/Sakhalin Leaf Warbler P. tenellipes/borealoides 10
Eastern Crowned Warbler P. coronatus 5
Zitting Cisticola Cisticola juncidis 1
Plain Prinia Prinia inornata 2
Reed Parrotbill Paradoxornis heudei 1
Crested Myna Acridotheres cristatellus 2
White’s Thrush Zoothera aurea 5
Dark-sided Flycatcher Muscicapa sibirica 1
Asian Brown Flycatcher M. dauurica 8
Blue-and-white Flycatcher Cyanoptila cyanomelana 16
Rufous-tailed Robin Larvivora sibilans 1
Blue Rock Thrush Monticola solitarius philippensis 1
Eurasian Tree Sparrow Passer montanus 100
Eastern Yellow Wagtail Motacilla tschutschensis 4
White Wagtail M. alba 4
Richard’s Pipit Anthus richardi 1
Yellow-breasted Bunting Emberiza aureola 1

WORKS CITED

(1) Alström, Per. 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.

(2) Brazil, Mark. Birds of East Asia. Princeton University Press, p. 358.

(3) del Hoyo, Josep, et al., eds. The Handbook of the Birds of the World. Lynx Edicions. Vol. 11, “Old World Flycatchers to Old World Warblers,” species accounts for Pale-legged Leaf Warbler (p. 663) and Sakhalin Leaf Warbler (p. 664) written by P. Clement.

Published by

Craig Brelsford

Craig Brelsford lives in Shanghai, where he runs shanghaibirding.com and studies Chinese at the Shanghai University of Engineering Sciences. Craig is the top-ranked (by species) eBirder in China, having noted more than 930 species. He is, in addition, the top-ranked eBirder in Shanghai, with more than 320 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 the diplôme d'études spécialisées en sciences de gestion from the University of Liege in Belgium. Craig has lived in Shanghai since 2007.

8 thoughts on “Pale-legged Leaf Warbler & the Shanghai Big 5”

  1. Nice blog, Craig!

    I have become convinced that I can now identify PLLW and Sakhalin on call, as a result of hearing two notably different calls on my local patch in Bangkok, and having listened to calls on known Sakhalins on Xeno-canto (e.g. the bird documented as Singapore’s first record a couple of winters ago). Furthermore when I visit Khao Yai National park in mid winter I hear PLLWs giving a consistently similar call.

    From what I can tell, PLLWs “tink” call is high pitched and slightly rising (like the bird in your recording above), where as Sakhalin’s call is a little slower, slightly falling in tone and sounds more “depressed”.

    These cryptic species plus the prospect of three Arctic Warbler taxa offer no end of entertainment on my local patch!

    Best regards

    Dave

    1. Hello Dave, and thanks for your valuable perspective from the Pale-Sak winter range! When you attain an ID based on call and examine your Pale-legged or Sakhalin, can you see any consistent differences in plumage or bare parts?

      1. Hi Craig, I have not seen any substantial difference in the plumage or bare part colouration of PLLW/Sakhalin, but field observations are always difficult as these birds are normally in shaded understorey, making judgement of colours very subjective; better to stick with vocalisations I think.

        My discussions with Phil Round indicate that he has not determined any plumage/bare part features to separate the two in the hand and he is working on wing measurements to identify to species (confirmed by DNA in a few cases when the species was first split), however there are some individuals which remain unidentified even in the hand as there is a zone of overlap in wing lengths.

  2. I find it hard to believe that we cannot determine a suite of characters to distinguish between the Pale-legged/Sakhalin species pair for non-singing birds. If this species pair was common in Western Europe or North America we would have long articles describing the suite of differences by now.

    HBW has this to say:
    P tenellipes (pale-legged)
    10–11 cm; 13.5 g. A medium-sized, short-billed brownish leaf-warbler with two buffish wingbars and distinctive pale pink legs.

    P borealoides (Sakhalin)
    11.5 cm; 10.7 g. A medium-sized leaf-warbler with long creamy-white supercilium and broad dark brown eyestripe.
    Distinguished from very similar P. tenellipes mainly by greener upperparts and lack of wingbars. Sexes alike. Juvenile undescribed.

    Ref Clement, P. & de Juana, E. (2016). Sakhalin Leaf-warbler (Phylloscopus borealoides). 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. (retrieved fromhttp://www.hbw.com/node/58890 on 28 September 2016).

    My postulates (completely unproven as yet, but my current working hypothesis) are:
    Through Shanghai in Autumn most pale/saks are Pale-legged, perhaps 80/20

    GENERAL SIZE

    Pale-legged: Compact, smaller than Arctic
    Sakhalin: Shape more like ECW or Arctic

    BILL

    Pale-legged: Shorter than Arctic Warbler
    Sakhalin: Longer, similar to ECW or Arctic

    CONTRAST OF NAPE WITH BACK

    Pale-legged: Sharp contrast
    Sakhalin: Nape colour merges gradually

    GENERAL COLOUR OF BACK

    Pale-legged: “Gold” toned greenish, even, no contrast in flight feathers
    Sakhalin: Much darker greenish grey with contrasting greenish flight feathers

    WINGBARS

    Pale-legged: Two clear brown bars
    Sakhalin: One, less clear less brown, whiter

    BEHAVIOUR

    Pale-legged: Feeds along thick branches and near to ground
    Sakhalin: Feeds higher, like Arctic-type

    Lots of work to do including ringing studies and lots of photos, but I do feel that perseverance will deliver a suite of usable characters.

  3. Hi Craig,
    Great work on the leaf-warblers, hope I can learn from this before my next China trip. My worst-nightmare are Emei, Claudia’s, Kloss’s etc in Sichuan.
    Sorry but not convinced that your falcon is a Peregrine, the head-pattern alone says juvenile Hobby to me. Will be interested to see if there are any similar comments.

  4. Very useful blog Craig, I never seem to get time to spot the subtle differences and most of my photos seem to miss the vital signs!
    I’m fairly convinced that the yellow warbler I photographed in Chengdu (and e-mailed to you in September) is the Grey-crowned warbler Seicercus tephrocephalus based on the information in the PDF you linked by Per Alström.
    I’ll have to trawl through my photos and compare with your blog and the PDF to see if I can positively ID any others.
    Your site provides a very useful resource, keep up the good work.

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