Pursuing Shanghai Birds in Alaska

alaska
Map of Alaska showing sites birded by Chris Feeney on his first expedition. In pursuit of Eurasian vagrants, Feeney ticked on U.S. soil species well-known to Shanghai birders, among them Lesser Sand Plover, Sharp-tailed Sandpiper, Wood Sandpiper, and Yellow-browed Warbler. He also noted species that breed in Alaska and are commonly noted on passage in Shanghai, among them Arctic Warbler and Bluethroat. The experience thrilled Feeney and caused him to begin making regular trips to Alaska. (Ian Macky/Craig Brelsford)

by Chris Feeney
for shanghaibirding.com

Feeney
Chris Feeney

I have been a birdwatcher almost my entire life. I was a career U.S. Army officer, spending 26 years in the military. I had a good bird list before I went into the Army. Once I retired from the military and a follow-on job, I started to seriously work on my life list. I birded places like Arizona, Florida, Texas, and California. I built my ABA list (American Birding Association, then covering the contiguous United States, Canada, and Alaska) to a respectable number—the high 600’s.

I knew that if I wanted to get to more than 700 birds, I would have to go to Alaska. I also knew that if I birded Alaska, I would have an increased chance to observe Eurasian strays.

This post is about my first trip in the fall of 2010. Areas that I will focus on are Gambell on St. Lawrence Island, St. Paul Island, and Nome on the mainland. In later posts, I will mention those three plus Adak in the Aleutian Islands.

The first Alaskan trip came about this way: At Cape May, New Jersey I met Mike Smith, a birder who lived in Anchorage, Alaska. He told me that if I made a trip to Alaska then I could base out of his house. He also said he would join me for part of the trip.

I started out in Nome in mid-August. Around Nome you can have everything from high tundra to boreal forest. Nome has three roads that go out about 70 miles (110 km). One goes east to Council, one goes west to Teller, and the other goes north into the wilds. The northern road is famous for having a small population of Bristle-thighed Curlew. They had already departed by the time I got to Nome. Several birds that are primarily Eurasian have breeding areas that carry over into Alaska. Arctic Warbler, Bluethroat, and Northern Wheatear nest in Alaska and then traverse the Bering Sea back to Russia and their wintering grounds.

I saw my first Arctic Warbler on the Nome to Teller road. On that same road I started to see groups of 4 to 6 Northern Wheatear. The road is 73 miles (118 km) long, and I saw wheatears over the entire distance. These birds were headed for the coast and their flight to Russia. I had hit the main fall migration push of these birds. I estimated observing several thousand birds, as I was never out of sight of them the entire way. I heard a Bluethroat on the Nome to Teller road, but it was skulking in thick underbrush, and I never saw it. My only other Eurasian birds around Nome were 2 juvenile Ruff that were on Safety Sound off the Nome to Council road.

My next stop was Gambell. Gambell is a small native village on the northwest side of St. Lawrence Island in the Bering Sea. Birders have access to about 10 square miles (26 sq. km) of the island, paying a fee to bird that area. Birders can access the entire island, but a much larger fee is required, and there is a requirement to have a local guide. All-terrain vehicles are a necessity, as the pea gravel makes moving quickly between sites impossible. ATVs can be rented from the locals. The only place to stay is the Gambell lodge—basic, but for birders it is good.

In mid-August Arctic Warbler were passing through, as were a few Northern Wheatear. I saw my first Bluethroat there as well. I was able to locate 2 Lesser Sand Plover. Little did I realize that Gambell would be a recurring spot in future Alaska visits and would add a significant number of Eurasian birds to my list.

Following Gambell I linked up with Mike Smith. We visited Homer and took the ferry to Dutch Harbor before flying to St. Paul Island in mid-September. A tour group was leaving on the same airplane that we flew in on. The tour leader told us that they had found Jack Snipe in one of the nearby marshes. Our tour guide took us out to the marsh and we found the Jack Snipe, a very unexpected bird. We then went to the Town Marsh, where Sharp-tailed Sandpiper had been seen. Adult Sharp-tailed Sandpiper take a normal route through Asia to their wintering grounds. However, a number of juvenile birds cross into Alaska before heading south. We found several in the Town Marsh. Another bonus bird for me in the marsh was Wood Sandpiper. Wood Sandpiper are fairly regular vagrants in Alaska, but in most places they are not seen every year.

That night a bad storm hit St. Paul. Winds were very heavy. The next day broke clear and with no winds. We started to land-bird. One of the better spots is Zapadni Ravine. It is a deep ravine with steep sides. Mike Smith took the top of the ravine on the right, I took the high side on the left, and our guide walked through the ravine on the bottom. Halfway through the ravine a small bird flushed and landed on a rock about 20 yards from me. I could hardly believe it; I was looking at a Siberian Accentor. This bird possibly had arrived on the winds from the night before, or it could have already been on the island. Regardless, it was a great life bird.

Later in the day we were at the northeastern part of the island at a place called Hutchinson Hill. In the past some very good birds had been found there, including Red-flanked Bluetail and Rufous-tailed Robin. We were approaching a small patch of wild celery when our guide said there was an Orange-crowned Warbler working in the celery. He then said that another bird was in the celery. I could not get on the birds. Then Mike Smith said, “Do you have kinglets here?” The guide had not answered when I got on the second bird. It was a Yellow-browed Warbler, the rarest Eurasian bird on the trip.

Mike and I went to Barrow in early October to see Ross’s Gull. They are fairly common if you can time your visit to their main feeding push. They cross the Bering Strait and feed in the Arctic Ocean before heading to their wintering grounds. We saw several thousand on our first two days at Barrow. Numbers dropped significantly after that.

So ended my first Alaskan bird trip. I was hooked on finding Eurasian strays after this trip, and even before I left I was planning my return.

PHOTOS

wheaters
Northern Wheatear on Nome to Teller Road, mid-August. The Northern Wheatear that breed in Alaska undertake one of the longest migrations of any songbird—more than 15,000 km (9,000 mi.) to the wintering grounds in sub-Saharan Africa. (Chris Feeney)
gambell
Town of Gambell, population 700, on St. Lawrence Island in the Bering Strait. A remnant of the Bering Sea Land Bridge, the island is closer to Asia than mainland Alaska—Russia’s Chukchi Peninsula is only 58 km (36 mi.) away. (Chris Feeney)
St. Paul Island
Wild celery habitat near Hutchinson Hill, St. Paul Island. Here Feeney found Yellow-browed Warbler, a rare vagrant to Alaska. Elsewhere on St. Paul, Feeney ticked rare vagrants Siberian Accentor and Jack Snipe and more regularly noted migrants Wood Sandpiper and Sharp-tailed Sandpiper. (Chris Feeney)
bluethroat habitat
Bluethroat habitat on Nome to Teller Road. Bluethroat breed in northern Alaska and the Yukon Territory in Canada. (Chris Feeney)

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Notes on Kamchatka Leaf Warbler, by Philip D. Round

by Philip D. Round
for shanghaibirding.com

Regarding the comment by Dr. Nial Moores in the shanghaibirding.com post Kamchatka Leaf Warbler in Shanghai: I would agree that both Arctic Warbler Phylloscopus borealis and Kamchatka Leaf Warbler P. examinandus may come through late, alongside each other, even in mid- to late May.

Here in Thailand, I think our earliest Kamchatka (diagnosed on wing length, greater than 70 mm) was 14 April, caught on Man Nai Island (12.015924, 102.283475) at the same time (so far) as our only undoubted Japanese Leaf Warbler P. xanthodryas.

While on average Kamchatka may be slightly larger-billed, and the respective sexes larger and longer-winged than Arctics, there is not much in it. Anybody who expects to be able to call birds one or the other in the field on anything other than voice is stretching credibility, I feel. Plumage overlap seems total. And of course on body size and wing length there is overlap between male Arctic and female Kamchatka.

The featured image above shows two individuals, with two photos each. Both were freshly moulted birds caught on northwards spring passage at Laem Phak Bia (13.050000, 100.083333), Phetchaburi, Thailand. Both were picked out as being slightly more brightly yellowish on underparts and on supercilium than typical spring borealis (caught on the same day), and brighter green above.

The bird in panels 1 and 2 was caught 14 May 2011. Measurements were wing 66 mm, bill 14.5 mm. On mt DNA (COI) we determined that it was examinandus. The identically bright-coloured individual in panels 3 and 4 was caught on the same day. Measurements were wing 62 mm, bill 14.5 mm. It was borealis on DNA.

The paper of which this comparison was a part is titled “Addition of Kamchatka Leaf Warbler Phylloscopus examinandus and Sakhalin Leaf Warbler P. borealoides to Thailand’s Avifauna.” It was published by the Japan Bird Banding Journal and is downloadable (708 KB) through shanghaibirding.com.

We record Kamchatka annually in Thailand, with most records in May. On average it is a later migrant than Arctic with (old specimen) records from Thailand and Malaysia even into the last days of May. Based on birds handled (and DNA assayed), I would re-emphasise that there is total overlap on the range of plumage characters with borealis.

Though we selected our first, unusually bright-plumaged “Arctic Warblers” in mid-May for assay specifically because they were a bit more yellow-green than usual, note that, just as in the panels above, some turned out to be examinandus and some seemingly identically bright birds were borealis.

Takema Saitoh at the Yamashina Institute has a little module that uses a canonical discriminant function that will separate most birds on biometrics. But of course, this is only good for birds that are handled. The key parameters are wing length, total head length (head plus bill), length of outermost primary, and length of tarsus.

As Craig Brelsford notes in his 6 June post, Kamchatka on average are a bit longer-billed. But even this did not reliably separate all birds unless one knew the sex (problems of overlap between female Kamchatka and male Arctic).

Call and song—so important!

Editor’s note: shanghaibirding.com has a growing library of resources on leaf warblers. In addition to the paper Phil Round directs us to above, we have the excellent presentation by Per Alström, “Identification of Phylloscopus & Seicercus warblers in China,” downloadable here (13 MB).

For even more of our posts in which Phylloscopus is mentioned, type “leaf warbler” in the search box nearby.
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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 29 Jan 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 24 Nov. 2019).

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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 24 Nov. 2019).

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 24 Nov. 2019).

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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Interesting WeChat Exchange on Arctic Warbler

by Craig Brelsford
Founder, shanghaibirding.com

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Shanghai Birding is the WeChat companion to shanghaibirding.com. In it, we exchange real-time reports and engage in discussions about birding in Shanghai and all China.

A discussion about Arctic Warbler showed the utility to birders of social media in general and Shanghai Birding in particular. Members Jonathan Martinez (based in Shenzhen) and Paul Holt (based in Beijing) shared their knowledge about Arctic Warbler and its sister species. In so doing, they shed light on the situation, still very imperfectly understood, of the Arctic-type complex in Shanghai.

Holt led off:

Paul Holt (PH): I see from a recent posting that @李伟 photographed an Arctic Warbler at Nanhui on the 28 October. Great images! Isn’t that extremely late? The latest ever Beijing record’s over two weeks earlier than that.

I then posted a long list of my Arctic-type records from autumn 2014 and autumn 2015. In the list, I bunched together all members of the Arctic Warbler Complex (Arctic Warbler Phylloscopus borealis borealis and P. b. kennicotti, Kamchatka Leaf Warbler P. examinandus, and Japanese Leaf Warbler P. xanthodryas). I list all three species because, although it is presumed that the majority of spring and autumn records in Shanghai are borealis, it is far from certain what the proportions are. (Arctic Warbler and its sister species are nearly impossible to separate on morphology but are distinguishable by voice.)

The latest autumn record I had of an Arctic-type warbler was 24 Oct. (2015).

Holt wrote back:

PH: Thanks @Craig (大山雀) Unless I’m missing something 28 October is later than any of the records you cite (but just by four days). Could it be that the Nanhui sighting is Shanghai’s latest ever? Also it’s interesting that you mention all three species. Have any of your region’s Arctic-types been identified to a species other than borealis?

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).
Leaf warblers are a tough group and are a perennial source of discussion in the Shanghai Birding WeChat group as well as on shanghaibirding.com. shanghaibirding.com has published a study of Shanghai’s Big 5 Leaf Warblers: (1) Pale-legged Leaf Warbler, (2) Arctic Warbler, (3) Eastern Crowned Warbler, (4) Pallas’s Leaf Warbler, and (5) Yellow-browed Warbler. (Craig Brelsford)

Craig Brelsford (CB): @Paul Holt I have not recorded anything other than borealis around Shanghai. (All confirmed borealis records are of individuals singing in spring.) I also suspect that a record of xanthodryas is next to impossible in Shanghai. I am aware that citing all three names is not a perfect solution. I list all three species because I believe information is insufficient. No one knows how many Arctic-type in Shanghai are borealis and how many examinandus. Very basic facts about the species in east-central China are unclear. Maybe someday studies will confirm that an Arctic-type in east-central China is borealis, with a probability of 99%. In that case, I would probably assign any silent Arctic-type I saw to borealis. Do you have any suggestions?

A few minutes later, I added:

CB: Just remembered that Michael Grunwell, Elaine Du, and I had Arctic-type this past Sat. 5 Nov. We got a good look at the bird, too. October was a warm, wet month in Shanghai, and the entire fall migration season seems to be late a week or two. Would others here agree?

PH: I’ve never seen xanthodryas in mainland China, have only ever encountered two examinandus (which were the first records for Liaoning & Hebei. Both sound recorded) here & have too little to go on I’m afraid @Craig (大山雀). Personally I log everything as Arctic Warbler by default, though that’s far from perfect. Until more of us work on this awkward group & make an effort to sound-record them, it’ll be a long time yet before a truer picture of their patterns of occurrence emerges. Cracking late record last weekend @Craig (大山雀). Surely that must be a good candidate for being the latest ever.

CB: @Paul Holt Maybe for simplicity’s sake I should log everything as Arctic. I have hesitated because I dislike speculation, and besides your very reliable records from up north I have little else to go on.

At this Martinez came in with his south-China perspective:

Jonathan Martinez (JM): I’ve heard xanthodryas on Fujian coast in early May and had a bird caught in October at Xitou identified as xanthodryas by DNA on tail feathers among about 15 borealis. I found an examinandus in central Guangxi in September, first suspected by call on a bird wave and clearly identified with call a few days later. I suspect examinandus is not a coastal migrant and probably goes through mainland China. I think still the only species recorded in Hong Kong is borealis, despite many looking for these.

CB: Thanks! With a confirmed xanthodryas in Fujian and examinandus only “suspected” not to use the Chinese coast, I’ll keep my clunky three-species listing. Arctic-type Warbler in China is a subject crying out for more research.
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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 has been noted in 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 “Pale-Sak” 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 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 Pale-Sak 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 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, June (02:00, 6.4 MB)

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

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 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
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 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.

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. (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, Pale-Sak 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 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 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 Pale-Sak 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: 29 Jan 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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