Friday, 8 September 2017

More head-scratching!

I'm spending way too much time looking at these troublesome stints! I only do it because (with a bit of patience) they will typically come close enough to point a camera at and photograph. Whether I'm learning anything or not (or, indeed, whether or not this constitutes a productive use of time) remains a moot point! With adult Red-necked Stints Calidris ruficollis now in a baffling array of 'states', I've been waiting for juveniles (which, you would think, as they are fresh, ought to be more 'consistent' in appearance). Interestingly, juveniles of Red-necked Stint are the last of the stints to arrive in Taiwan (a few juvenile Little Stints Calidris minuta have been present for a while now), but the first few (two) did show up today. With a nice juvenile Little Stint in the same group, the small flock I was watching today contained a total of three juvenile stints, all of which I was able to photograph. What was 'head-scratching' about them was that each one of the three looked about as different from the next one as did the other (though the third (left unstated but much-looked for) species was certainly not present). Of the three, the Little Stint perhaps stood out the most, with its leggy appearance, fine bill, and high rear end when feeding. Other features of this bird which were noticeable were dark-centred lower scapulars (though these were certainly not solidly black) and the obvious extension of the primaries beyond the tail, regardless of posture.

There is always a caveat that needs throwing in with these things, though, as the dark centres to the scapulars and wing coverts (a strong pointer towards Little Stint) had the magical property of being able to disappear almost completely in stronger sunlight!

The Little Stint was the second juvenile I found today, with the third juvenile being a 'good' Red-necked Stint. Although the bill of this individual is on the long side, its evenly-patterned head, subtle greyish-pinkish breast band (hard to make out due to the light being strong), and longish rear end all fit Red-necked Stint perfectly. The primaries fall about equal in length with the tail tip, perhaps a factor in making the rear end typically appear 'fuller' than in Little Stint, and just look at those lower scapulars! These are pale grey-centred, with even white tips ('perfectly manicured nails' as I have read somewhere), and nobbut a narrow black shaft streak at their centres.

Even though the lower scapulars in the Little Stint did manage to turn greyish-looking in strong sunlight, they never approached the obviously very pale grey centres of this bird. The pattern at the centre also differs markedly: a large, dark blob distally in the Little Stint and a fine shaft streak in the Red-necked Stint (with virtually no lateral expansion towards the tip of this streak).

Two straightforward birds today, then, a prototypical Little Stint and a prototypical Red-necked Stint, but these two did not start the day. Actually, the third juvenile was the one I found first, and it got me very excited for several reasons. Firstly, it had an obvious cap (unlike the other juvenile Red-necked Stint above) and (depending on the angle) the ear coverts often appeared dark. Secondly, it looked decidedly pot-bellied and dumpy, an impression exaggerated by the short-looking primaries which consistently fell well short of the tail tip, regardless of posture. Finally, it looked small-headed, and lacked the 'full' nape of most of the Red-necked Stints I have looked at recently.

It did have plenty of features of Red-necked Stint (and none at all of Little), including a breast band (which was strongly pinkish in the centre) and pale greyish lower scapulars with dark shaft streaks. However, unlike the Red-necked Stint above, most of the shaft streaks broadened distally into blob-shaped marks, some of which I think could perhaps be referred to as 'anchor-shaped'.

Although I never really thought that the bill looked sufficiently 'blob-tipped' to suggest the third (left unstated, but much-looked for) Calidris species, I became rooted to the spot after finding the second Red-necked Stint and seeing just how much this individual differed from that one. In fact, the second juvenile Red-necked Stint appeared so sleek in its proportions by comparison that it even managed to have a look of Ruff Calidris pugnax about it, and the 'mystery stint' looked about as different from that Red-necked Stint as it did from the nearby Little Stint.

It would be nice to be able to write that 'it didn't take long' for the party to be spoilt when I eventually managed to get shots of the spread toes. Unfortunately, however, that was not the case at all: it took several hours. The bird was forever in either water or in mud, and only on very rare occasions ventured onto 'higher ground' when its toes could be clearly seen. 

The lack of any webbing between the middle and outer toes means that this bird can only be a Red-necked or a Little Stint, despite its cap, potbelly, and short wings. As this bird has no real features of Little Stint and plenty of Red-necked Stint, it is therefore (unsurprisingly) the latter. It is perhaps just my luck that the first two juveniles I would run into this autumn would exhibit pretty much the maximum range of variation acceptable within the species. A learning curve, perhaps, but then why does the experience leave me walking away scratching my head wondering why I bothered to look at them in the first place? Above photos taken at Tu Cheng, Tainan City 8/9/17.

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