Eastern Yellow Wagtail - four taxa in a small field

I really like large white-headed gulls, also, I really like yellow wagtails. Not a great deal in common between the two groups you might think, however they are closely linked by the unhealthily high levels of frustration they can induce. I've already experienced it just trying to start this post. I dashed the title without giving it too much thought but doubts were starting to creep in before I'd put first word to page.


I don't believe there can be too much uncertainty about the second part of the title, at least not the "small field" part. Troublingly, there were a couple of Citrine Wagtails in the field and more than one mtDNA study indicates taivana and macronyx Eastern Yellow Wagtails share a common ancestor with Citrine Wagtail, and that they are more closely related to it than they are to the nominate tschutschensis! So the pedant might find room for a slightly raised eyebrow but following the broad tide of current taxonomic understanding I think it's safe to ignore the Citrines as far as this post goes.


Coming now to the first part of the title, the questions are more pertinent. Starting with what exactly is Eastern Yellow Wagtail, moving quickly on to what exactly is Western Yellow Wagtail and culminating with the crucial how do you tell them apart?


Yes, let's not beat about the bush, the unequivocal objective here is to get Western Yellow Wagtail onto my Japan list.


So to depart from popular convention; first the good news... It's actually quite easy to get Western on the list, though keeping it there may require a blinkered, if not a head in the sand, approach to modern taxonomy. The much respected Alstrom and Mild's Pipits and Wagtails tells us the large genetic difference between morphologically similar thunbergi (Western Yellow) and macronyx puts the latter firmly in the Eastern camp, however they also place plexa within the Western group, as "eastern thunbergi". So a tick? Ahhh, sadly no, there is afterall the lurking bad news. All major authorities have aligned within the last few years to include both these taxa within Eastern Yellow Wagtail. So that's that, isn't it?   Or is it...?


It strikes me the only thing for it is to get a bang to rights thunbergi in Japan. How hard can that be?


How hard indeed? That it isn't on the Japan list suggests there may be a modicum of difficulty.


The most recent edition of the OSJ list (2012) ,which doesn't recognise the split between Eastern and Western Yellow Wagtails, gives five subspecies as having been recorded in Japan, plexa ('accidental visitor' with five records), leucocephala ('accidental visitor' with two records), macronyx ('irregular visitor' to most of Japan but 'passage visitor' to Tsushima and the Danjo Is.), simillima (now usually synonymised with tschutschensis as 'passage visitor' to... well, the relevant parts of Japan from my perspective, ie migration islands and points west) and taivana (again, as 'passage visitor' to relevant parts of the country).


Ignoring the distinctive leucocephala and, for the moment, the commoner tschutschensis and taivana we are left with the thunbergi-like macronyx and plexa. So any claim of thunbergi needs to overcome the macronyx hurdle. How can this be managed?


Alstrom and Mild say of macronyx that "it isn't safely separable from thunbergi", well that isn't exactly encouraging, is it? But elsewhere they state "...there is considerable overlap in all these respects, and the majority are indistinguishable from thunbergi". Ah haa! Does not the majority are indistinguishable suggest a minority are morphologically distinguishable? So what are "these respects"? Hang-on, let me read further.


It turns out they cite other authors under "is said to differ..." and their own "examination of a long series of specimens". There is contradiction regarding upperparts.


We have macronyx "is said to differ" from thunbergi by:-
                                                    paler ear coverts
                                                    purer and brighter green mantle (Vaurie 1959)
                                                    deeper yellow underparts
                                                    more conspicuous wing bars
                                                    longer hind claw
                                                    darker (browner) less green upperparts (Stepanyan 1990) and
                                                                                                                   (Red'kin & Babenko 1999)
Then there's their own findings:-
                                                    cleaner grey forehead, crown and nape
                                                    blackish-grey lores not usually onto forehead contra thunbergi
                                                    blackish-grey ear coverts not reaching as far (usually smoothly
                                                    merging just behind eye, with slightly cleaner grey rear ear coverts
                                                    and neck sides)
                                                    slightly brighter upperparts
                                                    slightly cleaner yellow underparts (rarely shows necklace)
                                                    slightly wider, more clear cut and yellower wing bars
                                                    slightly longer hind claw


Obviously the first step is to scrutinize each and every macronyx I come across to familiarise myself with the commoner toxon, right? Err, no, the first step would be to find a macronyx, any macronyx. Despite what the OSJ may say about status, a bird this spring was my first (or, okay, probably second), macronyx ever. Whereas I've previously identified several plexa which according to the OSJ list had only five accepted records at the time of publication!


Have my identifications been in error or could the OSJ have got it wrong/be totally out of date? Incidentally, Alstrom and Mild cautioned against relying to heavily on currently published information regarding the migration routes and wintering areas of thunbergi and macronyx throughout Asia due to the difficulty of field identification. Here are some images of birds I believe to be plexa.

This was the plexa in the field on Tsushima in May this year. Rather distant but the dark ear coverts, the long, narrow and broken supercillium as well as the greenish greater coverts bar seem to be recurring features of birds I believe to be this taxon. 

One of several plexa in April on Yonaguni last year (2019), very similar in all respects to the above bird.



Another of the Yonaguni birds, the hind claw is outrageous.

By contrast the folowing are the only two birds I've seen that I believe to be macronyx, starting with the bird this May on Tsushima.

A presumed macronyx Eastern Yellow Wagtail on Tsushima, May 2020. 

It clearly differs from the above plexa by the absence of a supercillium, the white rather than greenish wing bars and the more strongly necklaced appearance. That said, I suspect this is a female due to the duller overall colouration than I'd expect from a male, particularly the washed-out upper breast and less bright mantle. Worryingly, this bird ticks all the thunbergi boxes given by Alstrom and Mild for the tentative separation from macronyx. The criteria given above referred to the comparision of males, thus I suspect a female macronyx versus male thunbergi may present an even more complex, if not insoluble, field identification conundrum.

This was the first plexa/macronyx wagtail I ever saw, a bird on Mishima a good many years ago. It was a total puzzle at the time and, though I tend towards macronyx nowadays, it could still go either way.

A heavier crop of the same shot. As with the earlier macronyx, the wing bars are white unlike(?) plexa but this bird has a trace of a supercillium. Alstrom and Mild state that it isn't unusual for female macronyx to show a narrow supercillium and this differs from that of plexa in that it's more prominent before, not behind, the eye. Red'kin & Babenko state female plexa is almost indistinguishable from the male.  

So there we are, things really aren't looking too rosy as far as getting Western on my list is concerned; in fact I'd say I'm out of options here. Clutching at the last remaining straw, might the IOC move the goal posts? Right, thought not.


Such small samples don't touch on how much individual variation might exist or how that may affect identification. Looking at the more common tschutschensis, there is considerable, if sometimes subtle, variation but it's hard to say whether this is individual, geographical or a combination thereof. A number of formerly recognised taxa are now gathered under the tschutschensis umbrella creating a whole new set of potential variables without needing to touch on the horror that hybrids could introduce to the mix.  

Most birds, of any age, should have completed or be close to completing pre-breeding moult at this time of year. The greenish tints on the rear ear coverts and nape should soon disappear as the tips of fresh feathers wear off. (Yonaguni, April)

A presumed female due to the overall dullness, it has the least loral black of any images I have (Tsushima, May).

By contrast, this was probably the darkest-headed bird in the field (May), I'd have liked to get a better view of the forehead in particular. And for variation's sake check if the median coverts are white. I've got plenty of tschutschensis images showing both white or green greater coverts bar but none as yet with a white median bar.

Even against the light the white sub-orbital ring and pale base to the lower mandible are obvious. None of my small macronyx/plexa sample show either of these features.

This was a rather arresting individual (Yonaguni, April) with its broken supercillium and extensively white throat. It also shows the white sub-orbital ring and pale base to lower mandible.

Same bird as above with probably the most extensively pale lower mandible I've noticed, not that I habitually check.

A very smart, clean and bright individual.

I suppose this could be called a bog-standard tschutschensis, if there is such a thing.

Then there's taivana, the straight forward member of the Eastern group of taxa. The first three images are of early May birds on Tsushima and the final one, which is very clearly in moult, on Yonaguni in April.

Some missing median coverts and tertials, the outer tails are still growing, it's surprisingly tatty overall. This is probably the least advanced bird I've come across on spring passage.

Did I start by saying I liked large white-headed gulls and yellow wagtails? Forget the wagtails, I'll stick to the far easier gulls.

awash with wagtails

Citrine Wagtail was a Japan tick for me on the Yonaguni trip and it almost didn't seem a surprise because there were simply so many 'exotic' wagtails on arable land and playing fields. In fact I saw a rather remarkable eight taxa. Arguably, the rarest taxon of all was lugens White Wagtail. I only saw a single individual of this, the default taxon in Kansai. I didn't see any Japanese Wagtails, the second most frequently encountered taxon here, only Grey Wagtail seemed in similar numbers to Kansai expectations.


I had frustratingly come across a possible Citrine earlier in the week. It had been mixed in with a flock of Eastern Yellow Wagtails on the rocks below the towering cliffs of the eastern headland but unfortunately the flock flew round the headland, impossible to follow without a boat (or wings). I went back over the next two days and though there were always about 30 Eastern Yellow Wagtails present I never again saw the possible Citrine.

A possible Citrine Wagtail, I got several equally bad record shots but the following image is the only clear shot I managed before the bird dropped out of view amongst the rocks. 

I've never seen a taivana with yellow cheeks like this and a pre-breeding Citrine seemed more plausible at the time. It's a pity I never saw the bird again.

The Kubura school playing fields are extensive and attract a lot of migrants, my only Greater Sand Plover, Dusky Thrush , Richard's Pipit and lugens White Wagtail were all here. The problem is birds tend to be distant but by some miracle the Citrine was not only the closest bird on this occasion but the closest any bird ever came.





A couple of minutes after leaving the school I stopped at the pond and no sooner had I done so than the Citrine followed me down. It was there for no more than three or four minutes then flew back towards the school. At the time I was unsure whether it was the same bird but after looking at the images, it clearly is. 

Taivana and tschutschensis were both very common, probably in equal numbers, more or less, with well over 100 birds seen each day if I went to two or three favoured spots. It wasn't until the seventh day (same as the Citrine) that I found my first thunbergi/plexa Western/Eastern Yellow, two of them in fact. Perhaps it was never likely to be a Western Yellow, but it was nice to dream for a while. The following morning I was able to catch up with one of them again and heard a typical Eastern Yellow flight call.

The vast majority of taivana weren't close to full breeding appearance yet but this one wasn't far away.

This individual wasn't too bad, most looked even more untidy than this.

My feeling was tsuchtschensis were more advanced, a small majority looked very smart whereas the same could be said of only a very small minority of taivana. 

These two plexa never came any closer than this but even at this range their appearance was striking because of the black mask and fine post ocular supercillium. 

The following morning one of them had made it to the road. There is limited white before the eye, which I hadn't been able to see yesterday, but the lores are largely black.

Neither Grey Wagtails (too common) nor the lugens White Wagtail (too distant) make it into this post. The other two White wagtail taxa were leucopsis and ocularis, the former was surprisingly scarce with only eight seen during the week while the latter was very numerous with well over 100 per day.

leucopsis

leucopsis

Typically distant ocularis on the school playing fields.

Black on the chin doesn't reach the bill on this bird, presumably it will soon. 

The huge numbers of wagtails that I infrequently to rarely see were a delight,they were widespread on the island, and but colourful and approachable. Collectively they were one of the highlights of the trip.

wagtails

A disappearing Forest Wagtail at Miike (Kyushu), 4 January 2008. It was really tough trying to digiscope this bird dashing around among the trees. This is the best result I got!

Forest Wagtails have turned up and even over-wintered in Kansai, however they're rare anywhere in Japan. There has since been another wintering at the same spot as the bird I saw at Miike.

Eastern Yellow Wagtails are a fairly common migrant in southern and western Japan, particularly in spring on off-shore islands. I see many on Mishima and Tsushima when they don't present a serious identification problem but I usually visit Hegura in October where they are both uncommon at that time and far more challenging to identify. I've never seen one in Kansai and given their preference for open habitat and conspicuous appearance this says something about their status in this area.
I've never even heard of Citrine in Kansai but unfortunately missed one found by Gordon Hay (visiting from the UK) on Hegura last October (2013).
In Kyoto Grey Wagtail is quite common in winter and can be seen along the rivers or on various ponds. In summer they mostly retreat onto mountain rivers and are less obvious.
Japanese and White (lugens) wagtails are resident and the latter also a very common passage and winter visitor. Japanese seems to have a closer affinity to water and is the commoner of the two on rivers in the city. Large numbers of White Wagtails can gather on the fields at Ogura (and other arable areas, especially close to rivers) and pre-roost flocks of 50+ birds can be seen flying into many urban areas in the region. I've also seen ocularis (East Siberian Wagtail) in Kyoto but it's rare, whereas I see quite a few each spring on islands such as Mishima or Tsushima in western Japan. I haven't seen leucopsis in Kyoto but I have seen a very good contenders for leucopsis x leugens hybrids here.

In winter, even the casual visitor should see White, Japanese and Grey along the Kamo River in the centre of Kyoto.

An autumn Eastern Yellow on Hegura, 19 September 2006.

One of several tschutschensis on Tsushima, 30 April 2012.

This taivana, on the same date and Tsushima location has just a hint of grey on the fore crown.

Another bird on the same date showing far more grey on the forehead as well as extensively on the nape, the supercillium has a distinct yellow tint.

This wintering Eastern Yellow in Kyushu (January 2015) reminds me of Dusky Thrush in this shot. 

A much different grey and white Eastern Yellow in the same field as the previous bird.

A winter Grey Wagtail on the Katsura River (Kyoto), 20 October 2010.

Another winter bird, January 2015.

A summer Grey Wagtail on Mt.Misen (Nara), 28 June 2013.

A splendid post-breeding male lugens on Hegura, 9 October 2009.

An adult male with a yellowish face, this is meant to be a feature of first-winters as far as I'm aware. Katsura River (Kyoto), 3 October 2013.

Non-breeding adult lugens on the Katsura River (Kyoto), 30 December 2010. 

First winter lugens on the Katsura River (Kyoto), 15 October 2010.

M.a.ocularis (East Siberian Wagtail) on Mishima (Yamaguchi), May 2008. The conspicuously dark-centred coverts aren't typical and something of a puzzle.

A typical 'East Siberian' on Iriomote, 2 April 2013.

'East Siberian' first winter on Hegura, 7 October 2011.

 

Putative lugens x leucopsis hybrid at Seika (Kyoto), 30 October 2008.

Winter adult leucopsis in Kyushu, January 2015.

A scruffy-looking moulting adult Japanese on the Katsura River (Kyoto), 18 September 2013.

Fresh adult Japanese on the Katsura River (Kyoto), 8 October 2012.

Adult Japanese Wagtail, 25 October 2014.