An interesting Chiffchaff at Spurn

I stayed at Spurn from 11th to 13th October with a regular group of friends, formerly from Leeds, namely; Roger Barnes, Vaughan Lister, Paul Doherty, Mick Cunningham, Richard Hart and Martin Quinlan whilst James Lowen also a friend originating from Leeds was with another group of birders from Norfolk. 
There were still several Yellow-browed Warblers around following the influx on Sunday 8th October but, other than an Olive-backed Pipit found on the 11th, few new birds turned up during my stay which was characterised by gale force warm, southerly or south-westerly winds.
On the 12th a tristis type Chiffchaff was seen and photographed at the Crown & Anchor late afternoon and I spent much of the following day looking for, and then watching it. This blog post deals with its identification.
A force 6 southerly wind blew throughout the day but one of the few areas that offered some shelter was the band of trees in the car park closest to the Crown & Anchor. The tristis type Chiffchaff was reported again here early on and when I arrived at about 9:00 a Yellow-browed Warbler was seen followed by brief views of a rather grey Chiffchaff.
Fortunately the Chiffchaff appeared to be on a circuit and every 30 minutes or so reappeared at the most westerly end of these bushes.
There were several birders present and it was interesting from the start how the appearance of the bird varied to different observers with some immediately dismissing it as nominate collybita. Of those who had seen the tristis Chiffchaff early on some were of the view that this was a different bird. As the Chiffchaff did a circuit and reappeared some considered that there was more than one bird involved including a typical nominate collybita and a paler bird!
The day started off heavily overcast but occasionally the sun shone through and this certainly altered the perception of the birds colouration as did the extent to which it was in shadow in the foliage.
To my eyes the Chiffchaff always looked greyish on the crown and mantle and especially so on the nape. Whilst the edges to the remiges and retrices were fringed olive green. The underparts were pale buff with a yellow tinge to the breast sides and undertail. The supercilium was prominent infront of the eye and also tinged yellow as was the upper eyelid. The legs were black as was the bill but with slightly paler sides at its base visible in the photographs but I thought it looked entirely black in the field.
Several observers commented that the overall impression of grey above and pale below with greenish fringes to the wings and tail was slightly reminiscent of the Bonelli's Warblers. 
The bird called repeatedly at times giving a slightly disyllabic hoo-eet which to my ears was fairly typical of nominate collybita. The noise of the wind in the trees put me off attempting to record the call although in hindsight any recording is better than none!
Photographs
I took photographs when ever the bird appeared during a couple of hours in the morning and a further hour in the late afternoon. Most of the time it was overcast but there was some sunshine when photo 4 was taken.

My camera, a Canon DSLR, is set on neutral so no sharpening or colour toning changes are made when the photo is captured. White balance is left on auto. On the computer I've made slight adjustment to the overall brightness of the image and sharpened them slightly but haven't altered clarity, vibrance or saturation. These images should be as close to how the bird appeared as Canon can make it.

Photo 1 

Photo 2 taken in shadow the bird looked darker above

Photo 3 the breast has some fine yellow streaks when seen close

Photo 4 taken with some sunshine the mantle looked slightly more olive and the fringes to wings and tail are brighter

Discussion
I posted Photo 1 on Twitter and got some helpful comments which directed me to a recent British Birds article (Vol 111 July 2018 pages 389-394) and other web resources which have addressed the identification of the races of Chiffchaff with particular reference to the use of DNA from trapped birds. The excellent and detailed summary by Alan Dean on behalf of the BB tristis panel is probably the best starting point for anyone with any interest in the racial identification of Chiffchaffs. Mick Cunningham also put me on to Vincent van der Spek's blog 'Turnstones' which has some interesting information on Chiffchaff ID from ringing studies in the Netherlands.
My initial thoughts were that the presence of yellow on the supercilium, breast sides and undertail plus the lack of chestnut/ brown on the ear coverts excluded tristis and that this bird was more likely therefore to be abietinus was a somewhat over simplified view given the latest published findings.
The appearance of abietinus is now thought to be much closer to collybita and there are few verified (by DNA) records in the UK. This is odd given that the range of abietinus is closer to the UK than tristis and one might therefore expect more records, unless their appearance is so close to collybita that they are overlooked. 
A 2012 paper in Dutch Birding (DB 34 (6) 386-392) provides results of mtDNA analysis of 41 birds trapped in the autumn of 2009-2011 which did not look like typical collybita (23 were identified as abietinus by the ringers handling the birds) or from very large birds, suggestive of abietinus. Of the 41, 11 were nominate collybita and 30 were tristis and no abietinus were identified in the group. 
At the Western edge of the range of tristis birds may show some yellow, particularly in the supercilium and these birds have been referred to as a separate race fulvescens. However, a 2017 publication by Shipilina (Patterns of genetic, phenotypic, and acoustic variation across a chiffchaff (Phylloscopus collybita abietinus/tristis) hybrid zone) concluded that genetic mixing of tristis and abietinus where the races are in contact is the source of plumage variation (chiefly occurrence of 'misplaced' yellow in the plumage) in tristis.
Conclusions
1. I know a lot more about racial variation in Chiffchaff and the identification of its subspecies than I did when I took the photos!
2. There was I think only one tristis type Chiffchaff in the area at the time and the appearance of the bird varied with the light and the extent to which it was shadowed by foliage. As demonstrated by the fact that birders stood close to each other had different pereceptions of the birds appearance.
3. The bird was probably an example of tristis/abientinus interbreeding often referred to as 'fulvescens'. These are birds from the western edge of the tristis range and are generally grouped with tristis and termed as Siberian type Chiffchaff and/or western tristis.
4. The call, to my ears at least, was typical for nominate collybita. Not sure how this fits in and I perhaps need to look in to call variation in tristis with the 'misplaced' yellow. 
5. A better starting point in the search for abientinus would be slightly larger nominate collybita with perhaps slightly greyer upperparts and less yellow underparts rather than odd tristis However, it appears that many abietinus may be inseparable from collybita in the field.   

Shetland Road Trip 25th Sept - 3rd Oct

Despite having spent more than 4 decades birdwatching in the UK I have never been to the Shetland Isles. So when Roger Barnes, a birding friend from Leeds, suggested a trip in late September I jumped at the chance. Roger already had a reservation on Fair Isle for 1st to 5th October where he was due to meet some friends so the timing of the visit was set around these dates.
There are a variety of ways to travel to Shetland and in the end we decided to drive in the camper and catch the ferry from Aberdeen to Lerwick. This gave us flexibility on the journey up and for our time on Shetland. We set off on 25th September with our first planned stop at Barns Ness, just over the Scottish border, where a 1st winter Woodchat Shrike had been showing well for several days.

Roger and I arriving at the aptly named Barns Ness

We arrived at Barns Ness in strong winds and overcast skies but there were a couple of other bird watchers in view and it turned out that they were watching the shrike and so were we within a few minutes of our arrival.

Woodchat Shrike 1st winter

A first winter Rose-coloured Starling had also been reported a few days earlier and in speaking to the locals we soon established that it was still present, feeding on the beach with Common Starlings. In the strong winds Starlings were flying in all directions but we persisted and eventually located the bird with about 30 Common Starling on the beach. Unfortunately the birds were flushed by another birder so we only managed rather distant views. 

Rose-coloured Starling with Common Starlings

The weather was forecast to improve later in the afternoon so we were keen to get to Musselburgh, our next stop.

Roger and I spent a week in Iceland in 2016 where we failed to find a regular summering White-winged Scoter so the opportunity to see a male that had been found in Spring this year was too good to miss.

Velvet Scoter - males

From the sea wall there were several groups of Velvet Scoter plus ones and two's spread over a kilometre or so. It looked like it might be a long task to search through them all but luck was with us again when we came across some local birders who had located the White-winged Scoter.

Once found, the pink rather than yellow, bill along with the swollen bill shape at the nostrils and large white tick behind the eye made it relatively easy to pick up, at least in good light.

White-winged and Velvet Scoter

White-winged Scoter

An adult Red-throated Diver moulting from summer plumage was feeding close to the seawall and provided a good photo opportunity.

Red-throated Diver - adult moulting from summer plumage

A Pectoral Sandpiper was also present on the nearby lagoons and we managed to locate this bird before dark and again the following morning where there were also two juvenile Curlew Sandpipers but all were distant telescope views.
From Musselburgh it was none stop to Aberdeen for our 7pm ferry to Lerwick. The wind was still blowing so the prospect of 12 hours on a rough sea was a little daunting but in the end the crossing was OK and we arrived on time in Lerwick.

Fulmar

The wind was still blowing westerly and there were few birds reported on Shetland so we did an initial tour of the southern part of Mainland calling at Sumburgh where we watched the Fulmars still occupying their nesting cliffs, Scatness where a Sabine's Gull was reported, Quendale and finally Levenwick.

Quendale Mill - scene of many rarities in the past

Here we had good views of a striking male Northern Wheatear which must have been of the Greenland race leucorhoa with rufous chest and tail with broad black band.

Northern Wheatear of the Greenland race leucorhoa

We stayed overnight at the Sumburgh Boating Club for £10 with electric, which would have been a great location at the mouth of the Pool of Virkie, had it not been for the gale force westerly which rocked the van all night.
The following morning we returned to Quendale which held a single Blackcap, then on to Levenwick where we added Chiffchaff and a Whinchat. News of a Common Rosefinch at nearby North Voxter took us slightly further north and after some great views of Twite the Common Rosefinch finally made an appearance.

Twite

Common Rosefinch - first winter North Voxter

We moved further down the coast to Sandwick for another Common Rosefinch and the coastal village of Leebitten became our base for the rest of our stay.

Leebitten in the foreground with the houses of Sandwick on the horizon

Common Rosefinch - first winter Leebitten

We were watching the weather closely but there appeared to be no sign of a let up in the west or north westerly winds. Our strategy was to find something scarce under our own steam. News of a White-crowned Sparrow on Foula joining the White-throated Sparrow found earlier in September was tempting but then came news of a River Warbler and Buff-bellied Pipit on Unst which already had American Golden Plover and Citrine Wagtail. In the end we decided to carry on covering the south Mainland area which, in hindsight, was probably a mistake and Unst would have been a better bet. Especially when a Pechora Pipit and Eastern Yellow Wagtail were found on 3rd October. We saw plenty of Wren of the darker, long-billed race zetlandica and had a good look at the Rock Doves which are probably as pure as any I'm likely to see in the UK.

Wren Troglodytes troglodytes zetlandicus (or borealis as classified by some)

Rock Dove

The wind continued to blow and we finally decided to give Fair Isle a miss, many of the planes from Lerwick were being cancelled and there was the prospect of being stuck for several days with no birds.
A pair of Snow Bunting at Grutness gave superb views as did a winter male Lapland Bunting nearby but we found nothing new. 

Snow Bunting

Lapland Bunting - ad male winter

A Marsh Warbler in Sumburgh quarry give brief views and we made a foray to Lunna at the north of Mainland where a Melodious Warbler had been found but the wind was so strong we struggled to stay upright and never located the bird which stayed for several more days.
On our final day we had decent views of Barred Warbler at Southpunds, made a final friutless search for a Blyth's Reed Warbler in Lerwick before having a look at the Black Guillemots in Lerwick harbour and heading for home.

Black Guillemot - adult winter

Overall we had a thoroughly enjoyable trip, and it was interesting to see so many famous places that have held major rarities in the past. It certainly felt like we could have encountered a rarity almost anywhere, but sadly we didn't!