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ON 16th December 2000, the late Dalston birder Barry Marrs phoned me with news of an extraordinary bird he had seen at Low Mill, Dalston. The bird was clearly an escape of some sort, and he could not find anything like it in any of his books. However, Barry had also found what appeared to be - potentially - a more interesting bird: a wintering warbler, which seemed to be a Chiffchaff, except for a curious call, most unlike the familiar call. Margaret and I were soon on site,
and by chance found the exotic perched in the top of an ash tree next to
the car; very startling it was too. (After reference to a variety of
sources, I finally located it in Birds of Hong Kong and South China
(Viney, Phillips & Lam): a Japanese Grosbeak, or Masked Hawfinch, Eophona
(Coccothraustes) personata.) This soon flew off, leaving us with time
to walk down towards the river, where we finally met up with Barry, who
had relocated his curious warbler. We then had intermittent views of this bird down to a few metres, as it fed about an area of tall weeds around a shallow pond, in alders nearby, and through patches of nettles, thistles and gorse between the pond and the banks of the river Caldew. For much of the time it was possible to keep track of the bird as it moved about by its call - a high, thin, flat, uninflected and tuneless ‘peep’, with much of the character of a very distant Dunnock’s call, although thinner and purer, and much feebler, so that often the bird was close when it sounded far away. Certainly it was not a call I associated with Chiffchaff - for that is what it surely was. In all respects the bird was a ‘plain Phylloscopus’ of Chiffchaff shape, size and behaviour, brown overall, and with little in the way of features. The upperparts were a smoky dull greyish mid-brown, faintly olive-tinged, becoming paler and ‘cooler’ grey-brown on the head. Cheeks and forecrown were slightly darker, making a faintly marked face-pattern: the supercilium was short, straight, diffuse and brownish, and there was strong narrow eyering. Underparts were dull buff, with very pale cream throat and belly, becoming white in the centre of the belly. There was a strongly greyish cast on the upper breast sides, almost meeting across the breast as a dull breast-band. Nowhere was yellow visible. However, the edgings of the flight feathers and less obviously the tail feathers were clearly - if finely - edged green, making quite a contrast with the dull colours elsewhere; especially in a rear view, the bird could momentarily look quite green - like a different bird, in fact. The greater coverts were diffusely edged, and more obviously tipped, pale buff-grey, making a diffuse wing bar. The bill was fine and all-black (typical of Chiffchaff) and the legs were very dark, looking black, although the feet were paler, and the soles quite bright orange. For a short time thereafter, this bird remained in exactly the same area, and was seen here by a number of other observers. Over the next couple of days, however, the bird appeared to forsake this area, and furthermore it soon became clear that nearby, on the settling tanks just north of Low Mill, were at least two other Chiffchaffs. The presence of these other birds, and the absence from its first-known area of the bird with the strange call, did much to confuse the picture. I returned a few days later, on 23rd December, and saw two Chiffchaffs feeding around the tanks or in adjacent alders. One of these was a typical-looking Chiffchaff which I assumed was of ‘our’ race, collybita, but I failed to get a good look at the other bird, and never heard any other calls. A search of the available literature concerning identification proved somewhere between inconclusive and downright contradictory. Some sources (e.g. Harris et al. 1989; Mullarney et al. 1999) claim that the ‘flat’ call - described as ‘recalling a lost chick’, excellently matching our bird - is reasonably diagnostic of the ‘eastern’, Siberian, race of Chiffchaff (tristis). Others (e.g. Beaman & Madge 1998), echoing Williamson (1962), report that this call ‘suggesting a distressed domestic chick’, while ‘usually attributed to abietinus [the Scandinavian race], is given by both forms [i.e. abietinus and collybita]’, whilst the Siberian race tristis has as its typical call ‘a plaintive rising ‘sweee’ or ‘peeep’, rather longer and more disyllabic than European forms [i.e. tristis and abietinus].’ The term ‘rising’ used here does not fit with the previously described ‘flat’ call, and appears to be a different call. Mullarney et al. mention that ‘in late summer-autumn, juveniles [of typical race] occasionally emit straight calls, ‘hiip’, which can then be confused with Siberian Chiffchaff’. Thus, unfortunately for the observer, there does not yet seem to be agreement between the experts as to whether this call is in any sense characteristic of any race, and if it is characteristic, of which race. It may be that the best that can be said of the Dalston bird is that whilst it was not of the ‘frosty’ appearance said to be typical of the eastern race tristis, the curious and striking call, and the overall cast of the plumage, coupled with green edges to flight feathers, and diffuse wing-bar, did match descriptions of some populations which are part of the cline of birds from northern Europe. As many readers will know, the wider ‘species’ of Chiffchaff with which we were familiar, has recently had several of its populations ‘hived off’ into new species: those of the Iberian peninsula, and the western Canary Islands, for instance, both have very distinctive songs, as well as differing habitat preferences, and plumage details. Both are now regarded, with justification, as separate species from ‘our’ European bird. Although there is some interest in the concept of birds of the more northern and eastern forms similarly being identifiable - as ‘Siberian Chiffchaffs’ - and perhaps regardable as a distinct species, the best that can apparently be said at the moment is that there is a cline between western, northern and eastern birds, which makes separation uncertain, and perhaps impossible. However, that being said, it would be most interesting to know the origin of locally-wintering Chiffchaffs. We know that our wintering Blackcaps tend to be of continental origin, many actually moving westwards, or even northwestwards, to find their wintering grounds with us; furthermore, many autumn vagrants to our shores - such as other Phylloscopus species - may elect, or be forced to attempt, to overwinter with us, having so-to-speak ‘run out of steam’ after migrating the correct distances to their normal wintering grounds, but in quite the wrong direction! Colin Raven (County Recorder) has kindly researched past county records of Chiffchaffs showing characteristics of the eastern forms, and has passed on details of five such records: Stainton, near Kendal, 25th December 1956; North Walney, 22nd October 1991; Millom, October 1992; Flookburgh Plain, February-March 1993; South Walney, 30th April 1995. Two of these are obviously of wintering birds, whilst the other dates would be typical of passage dates for a bird hailing from north and east Asian breeding grounds. It would be most instructive for members to try to obtain as much information as possible - including photographs and recordings - of our overwintering Chiffchaffs. We may eventually see a pattern of occurrence of particular types of birds. Jeremy
Roberts [In memory of Barry Marrs; see the tribute in CBC News Volume 12 Number 1, page 2] References Beaman,
M. & Madge, S. 1998. The Handbook of Bird Identification. Helm.
p 687
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