Sunday 2 May 2021

It's..., it's just a funny Stilt...

Way, way back..., long before Crick and Watson's leap forward began undermine the foundations of the BSC's concrete clarity, before digital photography condemned beloved note books (and, at times, careful observation?) to the dust bin. Way back when your brass 'n' glass monster wouldn't have known what to do with a screw-thread and 'a quality tripod' sounded more like a barrow boy's sales pitch rather than reference to essential birding kit... everything seemed so much easier. 

Well, didn't it? Think of warblers, they hadn't been split this way and that, the handful of large gull species presented little in the way of an identification challenge and Feral Rock Pigeons were just pigeons. Yes, altogether so much easier. Easier that is except for Dunlin. Do you remember the 'funny Dunlin'? 

Any potentially exciting wader you came across in the UK, were it a Semi(ish)P or a wide-of-the-mark Western was almost certain to be just a Dunlin. Albeit a 'funny' one. If I'd had 10 bob for every time I heard "I think it's just a funny Dunlin" when I was a kid, I'd have been travelling the country by taxi rather than hitching. But how often have you heard the expression "It's just a funny Stilt"? Not often? Well let's face it, when it comes to the Hard to Identify League, Black-winged Stilt is always going to be propping up the table along with the likes of Wrybill and Northern Lapwing, isn't it?

Or is it? 

I often wondered what might happen if there were splits in the stilt world. It was bad enough when 'Australian Stilt' was a vagrant subspecies to Japan. Particularly as I dipped one 30 something years ago and have been keeping half an eye on Black-winged Stilts ever since. But in time they were split (by the IOC), weren't they? So, having dipped on Pied Stilt (as is now) 30 something years ago is no longer the minor irritant it had been prior to the split.

No doubt in much of Eurasia where 'stilt' is still synonymous with Black-winged (himantopus), or elsewhere in the world where there's only a single taxon to worry about, you'll never hear anyone sigh "I think it's just a funny stilt". However, here in Japan there's a new "and exciting identification challenge" / "pain in the neck" to deal with and suddenly the straight forward stilt is rocketing up the Hard to Identify League table; indeed, a Champion's League place beckons. 

Believe it or not, and I personally I find it very difficult to be honest, there's the potential for three taxa in my local area! I'm informed by the 7th edition of the OSJ's official check-list that, as well as Black-winged, both Pied (leucocephalus) and Black-necked (mexicanus) are potentially in the mix. Pied as a vagrant to Japan and Black-necked is an introduced taxon in the Osaka area... worth letting that hang for a moment. 

That an alien species of stilt has been introduced is surely worth at least a post to itself but, to avoid the risk of getting lost in the weirdness of it all, I'll quickly move on. Suffice to say I've never seen one despite them (we are led to believe) being in Kansai. Nor have I ever even heard tell of one though, admittedly, it's not a hot topic round the village pump. Page 391 of the OSJ list if you don't believe me; I've looked numerous times and it's still there, directly below Crested Ibis. 

All the images I've seen of Pied and Black-necked from within their normal breeding ranges show birds that vary amazingly little in appearance. It's almost as if a single representative of the respective taxa has been given exclusive rights to publication. Are photographers so intent on getting (and posting) shots of the Mr/Miss Universe of the stilt world, or is it only Black-winged that's so incredibly variable? When I go down to my local lagoon I'm hard pressed to find two birds that look remotely alike.

Imagine my delight/horror then, when I recently heard there was a suspected Pied Stilt in Mie Prefecture, my adopted wader patch. Off I went hoping to see the living embodiment of those picture perfect denizens of the internet. 

I found the bird before sun-up. In fact I'd already found and photographed a Green-winged Teal (only my second in Japan) before that. Talk about a fast start to the day!

The Green-winged Teal was worthy of any search engines' top pick. A stonker! Now, if I were wise, I'd stop writing at this point... there are going to be tears.

A great start to the day.

Back to the inevitable reality. The stilt was never going to headline a Google search. This was clearly why it was billed as a possible Pied Stilt. But let me state at this point that I'm absolutely 100% certain this bird is Black-winged and not a Pied Stilt. With that out of the way, I can continue.

So, what are the features that might differentiate between a non-breeding Pied Stilt and the local shape-shifters? That's a question I should have been prepared to answer that morning. It's a question I wish I could answer now! 

According to Brazil's EAFG, it's marginally larger, with slightly longer, slightly uptilted bill and slightly shorter legs. A bird of slight margins it would seem. However, a quick delve into online resources seems to dispute the first assertation, indeed, slightly smaller seems a more popular description. I do find Brazil's descriptions extremely accurate as a rule, though leucocephalus is still considered a subspecies in the EAFG. "Slightly uptilted bill", I can believe this because so many Black-winged have slightly uptilted bills, not a lot to go on there. And "slightly shorter legs", how much shorter is "slightly shorter"? A bigger bird on shorter legs sounds reasonably distinctive, why then is it suggested only the call can be used to positively separate the two if non-breeding adults are involved? If the call is key to a positive identification, lets hope, unlike Black-winged, Pied doesn't have a wide range of calls...

I arrived at the correct lagoon (just along from the Green-winged Teal lagoon) at 05:00 (sunrise was 05:16 that day) and immediately saw three stilts below me from my seawall vantage point. One of them had a black nuchal patch and had to be the bird in question, or so I surmised. Unfortunately, the nuchal patch was rather tatty and the bird had a very obvious grey head, this wasn't at all what I'd been hoping for. Certainly not two stonkers in a row. Shortly after the sun came up, but hadn't yet climbed high enough to shed light on the birds, they flew to a far corner of the lagoon often used by roosting waders. This was both good and bad, mainly bad. It's always possible to get quite close to the birds here but in the early morning you're looking right into the sun coming over the seawall. In other words a great afternoon spot, a total waste of time on a sunny morning. Nevertheless, I drove round and got by far the closest views of the day.

Spotted Redshanks and Common Greenshanks were occupying all the decent rock piles and weren't about to let the lanky freaks get a toehold in the neighbourhood. Before too long the two BWS (the bird in question is now FS - funny stilt) flew back to the feeding area, calling typically as they went. The FS hung around for a couple more minutes before heading off in the same direction, loitering in the general vicinity of the cool-kids proved to be a pattern throughout the day. The two BWS could have made the synchronized stilting team but getting the FS side by side with the them was surprisingly difficult despite their close general proximity. And naturally, when it did fly back to the feeding area, it didn't call at all.

Thanks to the extensive head markings I was already resigned to this bird being a BWS, and not even a particularly funny one, but the call would have allowed me to leave and get on with other stuff. As things stood, I couldn't really leave just yet. I'd only seen it either before sunrise or with the sun directly behind it. I headed back to the seawall.

The FS at its closest all day. The grey head is disappointingly obvious. Is the bill "slightly long"? No, I don't think so. If slightly slender was a thing, we might be in business. It is uptilted though. Many BWS have uptilted bills but this is a fairly outstanding example, I rarely see birds with such a distinct uptilt, more often discernable tilt is limited to the lower mandible. This is verging on a kink, I'd place it at the Avocet-end of the BWS uptilt scale.

A pertinent question to ask might be whether the head is going to become paler or darker? The head and neck have the scruffy appearance of a bird actively in moult. As I've seen BWS sitting eggs in late May on this lagoon, it must be pre-breeding. I seriously doubt vagrant Pied Stilts arriving in Japan are from the extreme south of the range (though you never know), more likely they would be overshooting birds from more northerly breeding areas and as such presumably also pre-breeding. I have two big unknowns here though; where are the most northerly breeders and might they be more opportunistic breeders at their breeding latitude.

Skipping back in time to the initial pre-sunrise views from the seawall, the head is equally dark-looking even at that longer range. However, it hadn't merely been the black nuchal patch that had singled out this bird on arrival, it was surprisingly and intriguingly different in structure too, though I hadn't fully appreciated why at that time. The short legs were obvious from the outset, the bird was almost belly-deep in water most of the time. The question how much shorter is "slightly shorter" is even more pertinent. There was something else though and it wasn't until later in the morning that the penny to dropped. This bird is noticeably deeper- and shorter-bodied than the accompanying BWS. Shorter-bodied, at least in part, because of its shorter primary extension.

A couple of shots to provide context, the two uncontroversial BWS in the first and the FS in the second.

These two not only were not only aiming for the synchronized stilting team but were clearly from the same structural mold. The primaries almost always cloak the position of the tail, this is an occasion where the tail is visible (on the nearer bird) but hard to make out unless I crop the image much more. Nevertheless the primary extension can be seen to be significantly longer than on the FS. Those primaries look lethal. 

The FS belly deep in water showing of its non-lethal primary extension (the tail was invariably visible on this bird), deep body and uptilted bill. The nuchal patch is strikingly black compared to the saddle and the latter looking female brownish here but was strikingly, glossy green in life. 

As I mentioned earlier, there seems to be some contradiction on whether FS is slightly larger or slightly smaller than BWS. I can't speak to that but I can say that the deep-bodied appearance of this bird gives the impression of being slightly larger. However, when it comes to length, I'd judge it to be clearly slightly smaller. As it also tended to look smaller-headed, and is obviously shorter-legged, the balance is in favour of slightly smaller as far as this bird goes.  I wonder how 'size' has been gauged by those who have opined on Pied. Collection measurements? Direct field comparison? A combination? Gut feeling? And if you're wondering whether the FS is standing in a hole on the lagoon floor, it isn't, this is an accurate impression of the comparative leg length.  

Again, the same structural features are obvious; short legs, deep body (there was ever a greater expanse of white between wing and rounded keel) and short body, the latter due at least in part to the short primary extension beyond the tail. The short 'rear', pot-bellied look made me think of comparing a classic Pintail with Common Snipe. I watched these birds for hours and these features never varied, rendering the FS easily picked out with the naked eye in any situation. That said, and importantly, had the FS not been in the company of two uncontroversial BWS, I very much doubt whether I'd have noticed anything unusual about it. Seen alone, it would appear to be a standard BWS.

So there we have it, a stilt that would seem an unremarkable BWS if seen on its own but which morphs into a very eye-catching bird when directly compared to BWS. 

As I watched this bird for eight hours (05:00-15:00 with a couple of hours off for lunch, during which time I found two Little Whimbrels - great lunch) and filled an SD card with images, I can expand on the above basic appearance.

But first is the FS larger or smaller than the two BWS present? If you haven't already made up your mind based on the earlier images, here are a few more. Personally, I'm going for smaller based on naked eye views and on flight views which I have quite a few of. Nevertheless relative size is surprisingly ambiguous depending on angle and distance.

As I said, field views left me with the impression it was slightly smaller.

At whichever angle they were viewed, the primaries of FS looked shorter. Here the 'scissors' blades are less lengthy and the points resultingly closer together.  

Some shots of the legs up next.

I think the legs are not only short, which to an extent might be expected on a smaller bird, but they are also slightly proportionately shorter. This was most easily seen when birds sat, folding their long legs beneath them, and the vertical face of the back of the knee would fall less close to the end of the tail in the FS. This can also be noticed in some of the flight shots above, the base of the knee is closer to the end of the tail in the BWS.

There is one other feature that is supposed to be distinctive on a breeding Pied Stilt; the long 'mane' on the hind neck. What about Black-winged Stilts, do they also have a 'mane'? Most BWS don't have a black nuchal area and therefore any elongated white feathers on a white background might not be so obvious. If they do have a 'mane', how much shorter than that of Pied is it?

In answer to the first question, BWS does have a 'mane', at least the FS clearly does and it is a BWS. I don't have an answer to the second question.

Often, with the neck feathers lying flat there isn't a 'mane' to see on this bird, yet once the wind ruffles the feathers or if the bird erects the feathers, they become very noticeable. This particular bird is in moult and actually has a 'centre parting' down the middle of the neck so that when the feathers are raised there are two clear lines of long feathers.

The strengthening afternoon wind is parting the 'mane' into two lines with one side visible in this image. The feathers are quite long but also wispy at the base. More to come in a moment.

If the eight hours I spent with the bird already seemed more than enough, it wasn't. I must be a glutton for punishment because I went back a week later and spent another 10 hours with it. I needed to be absolutely sure about this bird, it seemed an educational opportunity. Interestingly, I felt the 'mane' had grown a little in the eight days between visits. Incidentally, the two BWS had left and this was the only Stilt present, though the lagoon was fast filling up with Common Greenshank, Spotted Redshank and Grey-tailed Tattler.

I think this shows a fairly obvious area of raised feathers, but presumably far less obvious than that of Pied.

The 'mane' disappears as the feathers are lowered. As the bird moved to a better angle with the light on it, the brown female-type saddle (mantle, scapulars, tertials and also the innermost two or three greater coverts) became an almost Northern Lapwing green; more obviously in life than in these images. This rather surprised me, I didn't expect a female could look so glossy. It didn't stop there, the contrastingly black wings had strongly purple/blue glossy greater coverts, I thought this was a male feature.

As with images of the saddle, the wings looked glossier in life than in these images.

Why did I spend a total of 18 hours watching this bird? Well, I was determined to get a recording of the call. I didn't hear it at all on the first visit. The second time I got two single call notes in flight early in the morning but it wasn't until 3pm (3pm!!!) that it finally started to call and I was able to get my recording over the next hour.

I can now state with absolute certainty that it's... it's just a funny Stilt.

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