Thursday 27 July 2017

The Topsham Stint

24th July 2017 - Topsham


edited 28/7/2017 - got date wrong.


I was starting to wonder if I should just pull the plug on this blog - no posts for six months and no signs of anything I really wanted to write about. Then a bird turned up and got us all scratching our heads. Opinions differed, I posted a few photos on twitter, some comments followed and I decided it was a good time to blow off the dust and write a new post.

The Background. In late afternoon 24th July the bird in question was found by Keith Birchall way out in the estuary on a rising tide. He made a few calls, I soon joined him and we watched a small Calidrid, clearly smaller than the accompanying Dunlin, white below and rather plain grey brown above with dark legs. This narrowed the possibilities: Little Stint (uncommon), Semipalmated Sandpiper (rare), Western Sandpiper (very rare) and Red-necked Stint (very rare). We couldn't make any further progress with the views we had but fortunately, as expected on the rising tide, it soon flew up the Clyst and was refound on the mud at Goosemoor. By then a few of East Devon's finest were on site and we watched it for another hour or so, at distances of 50-100m, before it flew off high to the south east. Surprisingly, given the relatively good views, no consensus was reached; some were happy to call it as a Semi-P, I was undecided.

I took some photos (below), adjusted for colour balance, sharpened and cropped but not resized. I also made notes shortly afterwards.

1. Calidris sp. 24/7/2017 Topsham

2. Calidris sp. 24/7/2017 Topsham

3. Calidris sp. 24/7/2017 Topsham

4. Calidris sp. 24/7/2017 Topsham

5. Calidris sp. 24/7/2017 Topsham

6. Calidris sp. 24/7/2017 Topsham

7. Calidris sp. 24/7/2017 Topsham

8. Calidris sp. 24/7/2017 Topsham

9. Calidris sp. 24/7/2017 Topsham

10. Calidris sp. 24/7/2017 Topsham

11. Calidris sp. 24/7/2017 Topsham

12. Calidris sp. 24/7/2017 Topsham

13. Calidris sp. 24/7/2017 Topsham

14. Calidris sp. 24/7/2017 Topsham

15. Calidris sp. 24/7/2017 Topsham

 Ageing. Clearly this is not a juvenile, the scapulars and tertials are fairly plain grey-brown with indistinct darker centres, a juvenile would show much more obvious paler tips to the scapulars at least and, at least on the uppers, more obvious dark or blackish centres. Also, it's not a breeding plumage bird, that would also show some blackish patterned scapulars and more obvious streaking and colour on the head and neck, even if worn. In fact it most recalls a winter plumage bird though perhaps with more diffusely darker feather centres - as in 1st winter. In theory, a July stint should be in one of two plumages - juvenile or breeding adult - this appeared to be neither. Ivan Lakin suggested a 1st summer and I agree this seems the case. A few 2nd calendar year birds - certainly Little, Semipalmated and Western, and possibly Red-necked do not show the usual summer feathers but moult into a plumage much like adult winter (Grant and Jonsson 1984; Veit and Jonsson 1987). Most 1st summers are thought to remain in the south on the wintering grounds but some certainly travel north with breeding birds. While this may explain the unexpected plumage it doesn't actually help much with identifying it, winter plumages (and presumably also 1st summers) are extremely similar in the four dark-legged species. On the plus side, Red-necked at least can probably be discounted on plumage at least; apparently all 1st summer Red-necked Stints in Australia during June to August show at least some rufous on the face and scapulars (Paton and Wykes 1978 per Veit and Jonsson 1987).

Structure. It was relatively slim, even sleek, with a rather long rear end, the wings looked quite long with tertials extending nearly to the wing tip - just a small primary extension. The bill was medium length, not obviously short like many Semi-P's or Red-necked and not long and thin like typical Western. On some photos it does give the impression of being deep at the base but I can't be certain. The bill tip did at times and very briefly suggest a slightly expanded tip but I could never be sure - it might have been mud or water drops; again the problem was that it never stopped moving. The legs appeared relatively long for a stint although maybe this was due to the warm weather, it certainly never looked short-legged and low-slung like many Red-necked. Since the two American species show partly webbed toes a good view of the feet should have helped. Despite looking no webbing was seen. The bird was constantly moving, often on mud or in water so it is, of course, possible we all overlooked this, but then nobody could say for sure the toes were unwebbed.

Plumage. I'm not convinced plumage detail is going to be much help but I'll describe it for the sake of completeness. Basically brownish grey (or maybe greyish brown?) above and white below. The crown was slightly darker and faintly streaked, the dark area did not appear to reach the bill leaving the forehead white - this quite markedly so at times. The supercilium was white and obvious behind the eye, above the lores it merged with the white forehead. The eye stripe was darkest on the lores and reached the bill base but did not appear to join with the darker crown. The ear coverts were only faintly darker apart from at the rear where a slightly more obvious patch was sometimes noted. The neck and breast sides were brownish grey and indistinctly streaked, not meeting across middle. All scapulars, wing coverts and tertials were brownish grey with slightly paler fringes and diffusely darker centres, all appeared relatively unworn though one or two longest (rear) scaps seemed to be missing.

Conclusions. It would have been so much easier if it had been a juvenile or a summer adult, the nondescript plumage could really fit any of three species (probably not Red-necked as explained above). I believe any chance of resolving what it was must rely on structure. I suspect an argument could be made for any species based on structure though I doubt it would be wholly convincing and largely comes down to probabilities; nevertheless I'll have a go. I think Red-necked unlikely as the bird looked rather too long-legged. Of the remaining three I would suggest Little is the best fit due to the slim, long shape with moderate primary extension (though hard to see exactly) and relatively long legs. The bill length and apparent shape could fit any though less typical of Western. No one saw any webbing between the toes but then absence of evidence is not evidence of absence. However, here are a couple of enlargements which may show something interesting.

16. Calidris sp. 24/7/2017 Topsham

16. Calidris sp. 24/7/2017 Topsham
These may show the outer toe or they may not, there's so few pixels it's impossible to be sure. If it is the outer toe then it definitely looks unwebbed, making it a Little Stint. It all comes down to interpretation, is that a toe or a stick in the mud?

Edit 28/7/2017. Should have thought of this before but the toe/stick question can be resolved by examining subsequent photos; here's photo 16 again and the next in the sequence.

16a. Calidris sp. 24/7/2017 Topsham

17. Calidris sp. 24/7/2017 Topsham

 There's nothing left sticking up in photo 17 as the bird takes it's next step so it's clearly a toe and not something in the mud, it also looks most likely to be the outer toe. It's nigh on impossible see exactly what's going on where the toes meet but it takes a lot of imagination to see any webbing/palmation; I think this is a Little Stint.

As always, other opinions are available and comments welcome.

A few references: the two classic papers on stint/peep ID (from European and North American perpectives and both featuring Lars Jonsson's superb paintings) are still the business after 30 years.

GRANT, P.J. and JONSSON, L. 1984. Identification of stints and peeps. British Birds 77: 293-315
PATON, D.C. and WYKES, B.J. 1978 Reappraisal of moult of Red-necked Stints in southern Australia.  Emu. 78: 54-60
VEIT, R.R. and JONSSON, L. 1987. Field identification of smaller sandpipers within the genus Calidris. American Birds 41: 213-236