A case study from Warwickshire, January 2013
A 'case-study' from Warwickshire, involving three individuals, one with evidently different appearance and 'fulvescens' traits.
© Dave Hutton
Dave Hutton has supplied excellent DSLR photographs of the Ladywalk Chiffchaffs and I am very grateful to Dave for providing plates 1 & 3. This photo, taken on January 27th, is strongly lit, which can reduce colour depth, but still captures the 'full colour range' of one of the two more-straightforward individuals. Note the visible texture across the scapulars and wing-coverts and the subtle colour gradations between different feather tracts. In duller light, the upperparts could appear relatively 'featureless', lacking any gradation between feather tracts and showing no highlights or colour-structure.
On January 1st 2013, Kay Donaghy, Ian Whitehouse and Martyn Yapp observed and heard 'a pale Chiffchaff with a Bullfinch-like call' at Ladywalk NR, in northern Warwickshire. They considered that it was tristis but, as views were brief, it was cautiously reported on newslines as a 'probable Siberian Chiffchaff'. Subsequently, three Chiffchaffs exhibiting characters associated with Siberian Chiffchaffs were located in the area (see below). They fed in ground vegetation, shrubs and trees but also in vegetation overhanging the banks of the River Tame, and this last habitat provided good feeding even during the heavy snow-falls of the third week of the month. The birds were occasionally elusive but quite regularly provided excellent views as they fed low down in vegetation along the river bank or in shrubbery adjoining the footpath. On some days at least two individuals called frequently, though on other days they could be silent for prolonged periods.
Photographs and sound recordings were obtained and a sonogram was produced from the latter.
To the eye, the appearance of Chiffchaffs will vary according to lighting conditions and background. Moreover, photographs are subject to quite extreme colour vagaries. Correspondingly, over-reliance should never be placed upon fleeting impressions or single photographs. With species such as Chiffchaffs, where allocation to form on the basis of plumage depends overwhelmingly upon subtle colour hues, judgements cannot be made in haste. Accurate evaluation of the full colour-range, for the eye and the camera, always requires adequate time and advantageous light conditions (neither overly dull nor overly bright). These factors were well-illustrated by these three individuals.
In the field, all three exhibited characters associated with Siberian Chiffchaff, such as a lack of evident olive in the crown and mantle and no evident yellow hues on the underparts. Their upperparts were grey-brown and their underparts buffy-white. In the field, there was no yellow visible in their plumage and the only evident olive was on the fringes of the remiges and rectrices. They appeared sometimes a little browner, sometimes a little greyer, according to the prevailing light conditions and the 'background' (for example they appeared greyer and colder when feeding against the grey flag-stones which line part of the river embankment). On dull winter days with low light intensity, the upperparts appeared rather featureless and 'monochrome'. Varying impressions were undoubtedly influenced by genuine differences between the three but closer and adequately prolonged observations of two individuals together, in more advantageous light conditions, revealed a warmer buff suffusion across the breast, along the flanks and on the vent (plates 2 & 3). Subsequently, high-resolution photographs by Dave Hutton revealed some slight olive streaks in the scapulars of at least one individual (plate 1). Irrespective of light conditions, one individual was evidently paler and greyer than the others (plate 4). Interestingly, this individual bore a ring on its right leg. Subsequently, it emerged that it had been trapped and ringed locally but, unfortunately, it had not been diagnosed to taxon level.
In summary, two individuals conformed with the currently designated features of Siberian Chiffchaff. This diagnosis was supported by recordings of the call (see below). One individual was paler and greyer than a 'classic' tristis and its diagnosis was correspondingly problematical.
© A. R. Dean
At closer range and with favourable and 'revealing'
lighting, the plumage exhibited subtle colour nuances and gradations.
In at least two individuals, a warmer 'tan' brown tinge to upperparts and a sandy-buff buff suffusion on underparts became evident.
© A. R. Dean
The only truly white areas were on the central belly and under-tail-coverts, which contrasted with a warmer buff wash across the breast, along the flanks and on the vent.
Examination of photographs of the ringed individual (plate 4) indicated traces of yellow in other areas of its plumage, including the supercilium, the sides of the breast and flanks, and the vent. The appearance of this individual, too, was subject to the expected level of variation with light conditions but it consistently appeared paler and greyer than the other two individuals. By mid to late January, it is quite possible that the plumage colours of this individual may have worn/bleached from originally richer hues. However, this individual lacked the tan-brown and sandy-buff tinges of the other two and it exhibited 'misplaced' yellow and olive.. Its pallor in combination with the extent of yellow suggest 'admixed' genetic origins. The combination of grey plumage and yellow streaking matches the characters of so-called 'riphaeus' types from the southern Urals.
© Dave Hutton
The ringed individual appeared paler and greyer, while this
photograph shows yellow streaks in the supercilium,
at the sides of the breast and flanks, and on the vent.
In the field all calls sounded like short, evenly-pitched monosyllables ('eeep' or 'iiihp') with a somewhat plaintive quality, thus matching Siberian Chiffchaff. The calls resembled one call of Dunnock or a straighter, higher-pitched and less fluted version of a Bullfinch call. Several recordings of calls were made on January 24th 2013. Generally it was not possible to determine which of the three individuals was calling and personally I did not certainly hear the greyer individual call. However, analysis of the recordings confirmed that all calls fell within the compass of currently recognised tristis calls but did include some slight variation. A series of calls can be heard here ►.
There are six calls in this sequence, at 1.7s, 8.5s (very quiet and easily missed), 10.7s, 15.7s, 20.4s and 25.7s. The calls at 1.7s and at 10.7s have been extracted and transferred adjacently to a new file here. Each call is very short (around 0.2s) and will sound very similar to most people. Those with a very good ear may detect that the first call has a 'straighter' (more even) pitch, matching the classic tristis profile, while the second has a slightly more arched, weakly inflected profile. Calls with a slightly arched profile (shallow 'sweeoo' calls) have been recorded from Siberian Chiffchaffs in western Siberia and on the wintering grounds in India (some more distinctly arched and 'disyllabic' than the second call of one of the Ladywalk birds).
A sonogram of the two calls from the Ladywalk bird(s) is below. See the Main Text for discussion and further illustrations of call variants, including the similarities and distinctions of arched 'sweeoo' variants given by various Chiffchaff taxa.
Figure 1. Two variant calls given by Siberian Chiffchaff, Warks, January 2013.