Booted Warbler at Sizewell: Dave Fairhurst (and Adam Rowlands

We usually include write-ups of some of the rare birds that turn up in Suffolk during the year – especially when it is a first for the county. this year we have descriptions of a few species that are real rarities but have occurred before in Suffolk.

David fairhurst found a Booted Warbler Iduna caligata at Sizewell on october 3rd 2020, with the bird showing briefly the next morning.

We have included here his description that was submitted to the BBrc (British Birds rarities committee). Maybe this could encourage others to submit birds in the same way to either BBrc or Sorc? We have also included Adam rowlands’ description which was submitted as back-up to David’s version. the three previous Suffolk (Watsonian) records of Booted Warbler are; Gorleston-on-Sea, September 3rd and 4th 1996, Landguard, october 16th 2011 and Lowestoft, September 6th and 7th 2018. i was interested in Adam’s final comments about some birders seeing a Garden Warbler Sylvia borin and mistaking it for the Booted. i was recently guilty of this regarding some pipits, when i saw what i wanted to see rather than what was actually there!

Ed.

Booted Warbler Iduna caligata, Sizewell, October 3rd and 4th 2020 Suffolk’s fourth record

David Fairhurst

Description

Saturday october 3rd 2020 saw light south-easterly winds, low cloud and drizzle on the Suffolk coast and it was soon clear that migrants were arriving. the feature of the day was thrushes and particularly Song thrushes Turdus philomelos, with an estimated 8000 arriving in-off the sea between Aldeburgh and Dunwich, mostly in the morning. interestingly the majority weren’t stopping on the coast but powering off high inland. earlier in the day, a rustic Bunting Emberiza rustica had been found in Lowestoft and a redbreasted flycatcher Ficedula parva at Landguard. i had spent the day birding the cliff-tops and bushes between Sizewell Hall and thorpeness and had had a great day, with an hour of light left i headed north to the Sycamores Acer pseudoplanatus and scrub just east of the A station at Sizewell. upon arrival at the Sycamores, i noticed a common redstart Phoenicurus phoenicurus and a eurasian reed Warbler Acrocephalus scirpaceus (both new for the day) and then a small warbler hopped up in gorse Ulex sp. bushes just a few metres away. this bird was different, instantly it was obvious it wasn’t a ‘regular’ species and going through a mental checklist i came to the conclusion that it was a Booted Warbler. the bird was favouring the northern most Sycamore and the low bushes and bracken Pteridium aquilinum around it.

Within just a minute or two of seeing the bird i had put the news out and rang the few local birders who i knew would be able to make it before dark. i had always thought that if i found a Booted Warbler it would be fraught, with brief views of a skulking warbler, gnashing of teeth and hours of searching. However, here in front of me almost continually on show with views ranging down to just 8 metres at times was a superb Booted Warbler. i have seen a couple of Sykes‘s Warblers Iduna rama but this species was quickly ruled out by the Sizewell bird by its having dark centres to the tertials, a relatively short tail and a dark tip to the spiky bill.

Several observers managed to make it to Sizewell that evening including Adam rowlands, Mike cartwright and richard Drew. the next morning the bird was present at first light, showing for just Mike cartwright and John Grant, before disappearing. it was a very nondescript bird and, therefore, rather difficult to write down the features; also, some colours changed as the light on the bird changed clearly a warbler, roughly a tiny bit bigger than a common chiffchaff Phylloscopus collybita but with a different shape – thinner, longer-tailed and bodied and a more spiky-billed appearance. the plumage was the most striking feature being very pallid brown with no olive tones at all; the brown was unlike the warmer orange-brown of a reed Warbler and several times i did consider that i was misidentifying it and it was in fact something like a Blyth’s reed Warbler Acrocephalus dumetorum or a Siberian (tristis) chiffchaff, P. c. tristis but they were quickly discounted and i kept coming back to Booted Warbler.

Head – an odd shape, strangely-domed/rounded (unlike Acrocephalus warblers which appear quite flat-crowned to me). A narrow pale-whitish supercilium was noted extending from the bill to just behind the eye but like several features on the bird this, at times, was hardly discernible

Bill – a pale, pinkish lower mandible with a dark tip, dark upper mandible

Legs – very thin and pale greyish, occasionally showing pinkish tones but variable depending on distance from the bird and background. feet slightly darker coloured than the legs

Upperparts – crown, nape, mantle and wings a pale grey-brown (a very unusual colour in a uk regular breeding bird context)

Underparts – (throat, breast, belly and undertail), grey-white in colour

Tail – similar colour to the upperparts but with dirty-white outer tail feather/s (not always visible and in fact only seen on a few occasions)

Adam Rowlands

Description

october 3rd had seen south-easterly winds and frontal rain providing ideal conditions for a fall of migrants on the Suffolk coast. i had spent the day searching for migrants between thorpeness and Aldeburgh and shortly after i returned home at 5.10pm i took a call from Dave fairhurst to say he had just found a Booted Warbler in front of Sizewell A Power Station. i immediately headed out and by 5.20pm i was with Dave and watching the bird.

Dave obviously takes the credit as the finder and identifier, but i have provided this as a supporting description. the following description was compiled shortly after my observations, which lasted about 15 minutes. frequently showing well. initially foraging low down in bracken, but moved into Sycamores where it spent some time in canopy (possibly as a consequence of the close presence of observers). relatively slow and steady movements when foraging, not hyperactive. feeding by leaf gleaning and brief fly-catching sallies. No obvious wing- or tail-flicking. No call heard. identified by structure, behaviour, strikingly pallid plumage colouration and bill pattern.

Size and structure: Similar size to a common chiffchaff, with structure most reminiscent of a Phylloscopus, but occasionally suggesting an Acrocephalus

Bare parts: Bill dark, with extensive pale flesh on lower mandible which showed a dark tip which was difficult to determine, but visible when viewed from below against dark background. Dark eye. relatively long, pale, greyish flesh legs – exact colour difficult to determine. Darker ‘ankles’ where tarsus joins toes.

Head: indistinct face pattern with dark smudge on lores and indistinct pale supercilium extending to just behind eye. Grey-brown eye-stripe, concolorous with crown and ear coverts

Upperparts: overall, a dull grey-brown, appearing very pale and pallid in dull light. When out in the open in bracken appeared more typically sandy, milky tea-coloured, but tone and colour varied with viewing angle and light conditions. Pale tips to greater coverts forming subtle impression of a wing-bar. Pale fringes to secondaries producing a ‘ghosted’ pale wing panel at some angles. Distinct dark centres to tertials visible when viewed from behind, but not so obvious when viewed in profile.

Underparts: Pale greyish-white, with no buff tones discerned by me in the dull light conditions. Dull-white outer tail feathers visible from below.

the bird was apparently still present at first light the following day and seen by a few observers. However, it was not reliably reported after about 8am when several observers were deceived by a Garden Warbler Sylvia borin feeding in the same area. As well as finding and identifying the Booted, Dave fairhurst was able to advise the observers of their error with the Garden Warbler. [the Booted Warbler breeds in eastern finland, eastwards across central russia to western Siberia, and from central and northern kazakhstan eastwards to western Mongolia and western Xinjiang province in china. it winters in northern and peninsula india as far south as the state of karnataka.

By the end of 2019 there had been 171 British records of Booted Warbler (British Birds 113, october 2020:626). the first record was on fair isle in September 1936, but the remaining 170 have all occurred since 1959.]