During October 2011, Chiffchaffs reaching St Agnes, Isles of Scilly, presented an instructive case-study in the variation among Chiffchaffs of presumed eastern origin, in the appearance of a classic tristis, and the confusion which genuinely 'grey and white' Chiffchaffs continue to present. During the third and fourth weeks of the month, Chiffchaffs reaching the island displayed a very wide range of plumages, with very significant differences in the amount of olive and yellow in the plumage and in their overall 'paleness'.

On October 16th and 17th reports of 'pale Chiffchaffs' came from both the Troy Town and Lower Town areas, with suggestions in each case that the birds were 'Siberian Chiffchaffs'. However, the appearances of the two were radically different. Fortunately, both remained for several days, which enabled observers to make careful assessments of plumage and calls, though both called rather infrequently.

The individual at Troy Town proved to be a classic (even 'ultra-typical') Siberian Chiffchaff Phylloscopus collybita tristis, in terms of 'brown and buff' plumage and evenly-pitched, plaintive call. Very much in contrast, the Lower Town individual proved to be an archetypal 'grey-and-white' Chiffchaff, with plumage hues very reminiscent of a Bonelli's Warbler P. orientalis / P. bonelli and with calls typical of collybita and abietinus. It (or a near-identical individual) later relocated to ivy clothing a wall near the Parsonage, where very detailed observations and close-up photographs were enabled.

Thus, with the concurrent presence of a 'brown-and-buff' tristis giving the classic Siberian Chiffchaff call, and a 'grey-and-white' Bonelli's-like Chiffchaff giving Common Chiffchaff calls, many of the elements of the 'tristis issue' were encapsulated on this small island during mid-October 2011.

The Siberian Chiffchaff

The individual at Troy Town was first observed on October 16th by Derek Pratt, whose attention was drawn by the unfamiliar call, and he alerted Steve Addinall and Ken Shaw. From the information conveyed by Derek, Ken and Steve suspected that the bird might well be a Siberian Chiffchaff. Steve, who has a particularly good ear, quickly picked out the call and immediately equated it with recordings of tristis to which he had listened previously. He likened the call to that of a Dunnock rather than to the often-cited Bullfinch, which agrees with my own interpretation. Subsequently, the bird frequently fed out in the open on the ground in one particular field, which enabled prolonged and detailed observations by many birders. It proved to be a classic 'brown and buff' Siberian Chiffchaff. It remained until the 19th and photographs were taken by various observers. As the tristis fed frequently on the ground, the neutral grey of the soil gave full emphasis to the brown and buff hues, which can easily become diluted when a bird is viewed against the sky or in overly severe light. I am indebted to Robin Hemming for permitting me to include three of his excellent images, which were taken in soft, late-afternoon light on October 17th. A fourth image, one of my own, was taken mid-morning on October 18th. It is of lesser quality but is included to illustrate the slight variation in hues resulting from brighter lighting.

The Siberian Chiffchaff displayed no olive in the crown and mantle and no yellow away from the bend of the wing. In addition to these 'starting point' features for tristis, it also displayed a distinctive grey-brown hue to the crown and mantle and a warm buff wash to the supercilium, cheeks, and the sides of the breast and flanks (Plates 1a to 1d). This suffusion was richest on the fore-supercilium and cheeks and, in sunny conditions, it could take on a rusty or even pinkish hue.  The characteristic grey-brown and buff hues in the plumage recalled Mountain or Caucasian Chiffchaff P. lorenzii or even Booted Warbler Iduna caligata. The legs and bill were 'densely' black and the latter rather delicate. It required considerable patience to hear the bird call but, when it did so, the call was again classic tristis: a monosyllabic, evenly pitched 'eeep' or 'iiihp', fading at the end and with a characteristic plaintive quality.

Plate 1a

© Robin Hemming

Plate 1b

© Robin Hemming

Plate 1c

© Robin Hemming

Plate 1d

© A. R. Dean

Compare the images above with photographs in the Gallery, which include unequivocal Siberian Chiffchaffs in Siberia and Kazakhstan, and also with photographs of a Siberian Chiffchaff trapped at Ottenby Bird Observatory, in Sweden, in early November 2011.

The 'grey-and-white' Chiffchaff

On October 16th a 'very pale' Chiffchaff was reported near Lower Town, with suggestions that it was a Siberian Chiffchaff. When other observers caught up with this bird it was immediately evident that it did not have the necessary feature-set of a diagnosable Siberian Chiffchaff. Rather, it was a good example of a 'grey-and-white' Chiffchaff. During prolonged observations on October 16th and 17th, this individual called several times, uttering both a rising 'hweet', typical of collybita/abietinus, and also a rising and falling, sharply inflected 'sweeoo'. At no time did it use a tristis-like call. On October 27th and 28th, a similar (perhaps the same) individual was seen at very close range (down to 3 or 4 metres) near the Parsonage and also behind the old observatory buildings. For observers for whom nominate collybita is the norm, it was indeed an arresting individual, with a dominant pale grey component to crown and mantle, markedly white underparts, bright green fringes to remiges and rectrices, and paler fringes to tertials. At such close range it was determined that there were, in fact, a few fine olive streaks in the mantle and a slight yellow tinge to the upper part of the eye-ring (Plate 2e). There were the inevitable slight variations in hues depending upon light conditions (from semi-shade to bright sunlight) and the bird's surroundings (Plates 2a to 2d);  yet the strikingly grey-and-white body plumage and bright olive-green (even yellow-green) fringes to the remiges were consistent in its appearance. The face pattern (with well-defined eye-stripe and broken eye-ring), very short primary projection and slight, all-dark bill were clearly those of a Chiffchaff;  however, the plumage hues of Chiffchaffs which are so strikingly grey-and-white (in a UK context), and often with bright olive fringes to the remiges, could very easily be confused with those of one of the Bonelli's Warblers  P.bonelli / P. orientalis. On October 28th it was heard to call, using a rising 'hweet' typical of collybita/abietinus.

On the basis of their pale and grey appearance such individuals have often been claimed as tristis but, in fact, they are phenotypically rather distant from a core-range Siberian Chiffchaff, and much closer in appearance to less-colourful examples of abietinus, particularly from the east of that form's range (Kees Roselaar and Lars Svensson in litt.). The form abietinus appears to exhibit particularly wide individual and geographical variation. To British observers, for whom nominate collybita is the norm, paler examples of abietinus can seem perplexingly different from a typical collybita. However, Chiffchaffs which in a British context seem strikingly 'grey and white' may appear less remarkable when compared with less colourful examples of abietinus. When such 'grey and white' Chiffchaffs give an abietinus call, as with the Scilly individual, there seems little reason to suspect that they are not abietinus. However, a few 'grey and white' Chiffchaffs give a tristis-like call. It seems likely that such individuals originate from the overlap zone between the ranges of abietinus and tristis, in the region west from the southern Urals, where hybridization has been inferred. For fuller discussion and comments on the problems which arise in the overlap zone, see the main text.

Plate 2a.

© A. R. Dean

Plate 2b.

© A. R. Dean

Plate 2c.

© A. R. Dean

Plate 2d.

© A. R. Dean

Plate 2e. Enlarged detail, showing yellow tinge in upper part of eyering.

© A. R. Dean

Plate 3