SIBERIAN
CHIFFCHAFFS Phylloscopus collybita
tristis AT POWICK SEWAGE TREATMENT WORKS, DURING THE WINTER 2014 – 2015
The winter 2014/2015 proved exceptional for the
numbers of Common Chiffchaff Phylloscopus
collybita at Worcestershire’s sewage treatment works, with three prime
localities in the south of the county, Powick, Upton-upon-Severn and Kempsey
holding a combined estimated total of 45 – 50 individuals.
Powick proved the most productive and by late
December, two Siberian Chiffchaffs were discovered feeding on the filtration
beds and along the adjacent hedges. Fortunately both individuals were often
very confiding, allowing an excellent opportunity to obtain detailed analysis
of the birds’ plumage, moult strategy and vocalisation. Though generally, the
plumage colouration was similar on both birds, distinct differences were
reasonably obvious, allowing easy separation in the field and the following
article specifically deals with these variations, the timing of their
pre-breeding moult and finally vocalisation.
Plumage
& bill colour variations
Underparts, face & bill
Bird 1 (from now
on referred to as the dark-billed bird). Plate 1
This individual showed a distinct buff wash to the
breast, flanks and thighs, plus a faint buff wash on the shortest
undertail-coverts, whilst the throat, belly and longest undertail-coverts were
predominately white. The supercilium was pale buff throughout, the eye-ring
whitish, the ear-coverts rusty-buff and a darker brown eye-stripe was prominent,
particularly before the start of the pre-breeding body moult. Any traces of
yellow were restricted to the underwing-covers and axillaries and the bill was
dark throughout. Its appearance matched a so-called ‘classic’ Siberian
Chiffchaff.
Bird 2 (from now
on referred to as the pale-billed bird). Plate 2
The ear-covert and underparts colouration was pretty
much identical to the dark-billed bird, whilst the supercilium, though
predominately buff, showed a hint of yellow just above the eye and on the upper
eye-ring, being quite obvious on the right side of the face, but far less so on
the left. The eye-stripe was lighter and far less prominent, plus the bill was
pale along its cutting edge and at the base of the lower mandible. The trace of
a yellow tinge above the eye and possibly the extent of yellow on the bill
suggests this individual to be a bird from the western breeding range of tristis, which can show limited amounts
of yellow on the upper eye-ring, supercilium and underparts and has been
assigned the form ‘fulvescens’
(Severtzov 1872). The origins of this additional yellow compared with a
‘classic’ tristis are debated. It may be simply individual or clinal variation
or may indicate slight introgression from abietinus
populations. Such individuals are generally treated as a variant of Siberian
Chiffchaff and the term ‘fulvescens’, while a convenient designation, has no
formal taxonomic significance.
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Plate 1 - Siberian Chiffchaff (dark-billed bird). Left: 21st February 2015. Right: During pre-breeding moult, 22nd March 2015. © Andy Warr
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| Plate 2 - Siberian Chiffchaff ‘fulvescens’ (pale-billed bird) 21st February 2015. © Andy Warr |
Upperparts & remiges
Dark-billed bird.
Plate 3
Brown-grey on the nape, mantle and scapulars, the
latter having very limited olive-green streaking, whilst the crown was a darker
uniformed brown and a slight olive-green tinge was present on the back, rump
and uppertail-coverts. The greater-coverts were broadly tipped buff, forming a
distinct, but diffuse wing-bar, the wing-coverts, primaries and secondaries were fringed olive-green
and contrasted with the broad buff fringes to the tertials and buff tips to the
primaries.
Pale-billed bird.
Plate 4
A paler sandybrown-grey on the crown, nape, mantle and
scapulars, with a slight olive-green tinge to the latter and only a hint of
olive-green on the back, rump and uppertail-coverts, so little contrast with
the mantle. The greater-coverts and tertials were buff fringed, plus the
primaries tipped buff, like the dark-billed bird, but the primaries, secondaries and lesser wing-coverts
were edged a brighter olive-green.  |
| Plate 3 - Siberian Chiffchaff (dark-billed bird) 21st February 2015. © Andy Warr |
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| Plate 4 - Siberian Chiffchaff (pale-billed bird) 21st February 2015. © Andy Warr |
As well as plumage and vocalisation, the timing of the
pre-breeding moult is a good indicator, when determining the identification of
Siberian Chiffchaff. In the winter quarters, a partial moult is carried out
prior to the migration north to the breeding grounds and includes body feathers and sometimes the
innermost tertials and central tail feathers.
The timing of this moult varies between the races,
with nominate collybita being from December
– January (Ticehurst 1938; Williamson 1967; Ginn & Melville 1983), abietinus from January – mid-February
(Ticehurst 1938) and tristis from mid-February
to the end of March (Ticehurst 1938).
Plates 3 & 4 above, depict both individuals before
the pre-breeding moult on 21st February, holding a full set of tertials and
central tail feathers, plus uniformed sleek body feathering throughout. By 14th
March, both had dropped their inner and middle tertials, plus the central pair
of tail feathers, whilst the first signs of body moult were apparent,
predominately on the head and underparts.
Dark-billed bird.
Plates 5 & 6
Note the missing inner/middle tertials depicted in
plate 5 and signs of body moult around the face and on the underparts in plate
6.
Pale-billed bird.
Plates 7 & 8
Timing of the moult was almost identical to the
dark-billed bird, except for the growth of replacement tertials and tail
feathers being more advanced, with the middle tertials just visible beyond the
scapulars and the central tail feathers about level with the longest
uppertail-coverts.  |
| Plate 5 - Siberian Chiffchaff (dark-billed Bird) 15th March 2015. © Andy Warr |
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| Plate 6 - Siberian Chiffchaff (dark-billed bird) 15th March 2015. © Andy Warr |
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| Plate 7 - Siberian Chiffchaff (pale-billed bird) 14th/15th March 2015. © Andy Warr |
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| Plate 8 - Siberian Chiffchaff (pale-billed bird) 14th March 2015. © Andy Warr |
Dark-billed bird. Plate 9
By 21st/22nd March, the new central tail feathers are still hidden below the uppertail-coverts, but the middle tertials are clearly visible, whilst the tips of the innermost pair are only just protruding beyond the scapulars.
Pale-billed bird.
Plates 10 & 11
The central tail feathers and both the middle and
innermost tertials are approximately ¾ grown, whilst there is heavy feather
moult on the cheeks by 21st March.
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Plate 9 - Siberian Chiffchaff (dark-billed bird) 21st/22nd March 2015. © Andy Warr
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| Plate 10 - Siberian Chiffchaff (pale-billed bird) 21st March 2015. © Andy Warr |
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| Plate 11 - Siberian Chiffchaff (pale-billed bird) 21st March 2015. © Andy Warr |
Vocalisation
Typically, Siberian Chiffchaffs are frustratingly
silent on the wintering grounds, which seems unusual considering Common
Chiffchaff collybita is so vocal. Despite
over 40 hours spent with both individual between late December - early March,
the pale-billed bird was heard just once, whilst the dark-billed bird remained
silent until 14th March. Hereafter, they became a little more vocal and was
soon apparent that as well as the classic tristis
call, two distinct variant calls were included in both birds vocabulary.
Unfortunately neither turned out to be singing males.
Dark-billed bird
(sonograms)
Call 1- A slight variant of the classic even pitched ‘peet’ call of tristis, being an near-monosyllabic ‘sweeoo’, marginally rising in
pitch at the beginning, levelling out at 4.3 kHz, before dropping to 3.6 kHz.Call 2- A loud, straight, almost monosyllabic note, rising in pitch from 3.2 kHz - 4.9 kHz, then a slight fall in pitch towards the end.
Call 3- A much quieter, thinner call compared to the latter and structurally more similar to the rising disyllabic ‘hweet’ call of Common Chiffchaff collybita/abietinus. The call ranged from 3.1 kHz – 5.3 kHz.
Pale-billed bird
(sonograms)
The tristis ‘peet’/’sweeoo’ call was heard on two
occasions, but eluded the recorder. Calls 1 & 2- These two are subtle variants of the same call, being very similar to call 2 of the dark-billed bird in volume, pitch and structure, though slightly brighter and sharper in tone. Call 1 had a shallow drop in pitch at the beginning, whilst this is lacking in call 2. Both calls ranged from 3.2 kHz – 5.2 kHz.
Call 3- Identical to call 3 of the dark-billed bird in volume and structure, but ranged from 2.8 kHz – 5.5 kHz.
All calls from both individuals were reasonably
consistent in length, ranging from 0.13 – 0.15 of a second.
Recordings of the calls
Dark-billed bird- Call 1Click here Call 2Click here Call 3Click here
Pale-billed bird- Call 1Click here Call 2Click here Call 3Click here
For further comments on call variation in Siberian Chiffchaffs see Alan Dean’s web items Click here and Click here and for Martin Garner's web item Click here
For more photos of the Powick birds, visit my
flickr page Click here
Acknowledgements
Many thanks to Alan Dean for his input and advise during the production of this article.
Written and compiled by Andy Warr.
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SIBERIAN
CHIFFCHAFF Phylloscopus collybita tristis
AT GRIMLEY, WORCESTERSHIRE IN APRIL 2015
On 22nd April 2015, a singing Siberian Chiffchaff was
discovered by Brian Stretch at Camp Lane Pits, Grimley. The bird remained
onsite for a couple of days, favouring a stretch of partly submerged Willow
along the eastern shore of the southern pool and like the Powick birds, gave an
excellent opportunity to study both plumage and vocalisation.
Plumage
& bill colouration
Upperparts, remiges, rectrices, face & bill
Plates 1 & 2
The crown, mantle, scapulars, back and uppertail-coverts were a uniformed brown and lacked any obvious olive-green flecking throughout, whilst the rump possessed a slight olive ting and the nape had a greyer cast. The greater-coverts were fringed buff/off-white, the tips forming a narrow, diffuse wing-bar and the remaining wing-coverts, primaries, secondaries, tertials and tail feathers were also fringed/tipped buff, with only the slightest hint of olive-green present, so minimal contrast in colour between the remiges/rectrices and the upperparts.
The crown, mantle, scapulars, back and uppertail-coverts were a uniformed brown and lacked any obvious olive-green flecking throughout, whilst the rump possessed a slight olive ting and the nape had a greyer cast. The greater-coverts were fringed buff/off-white, the tips forming a narrow, diffuse wing-bar and the remaining wing-coverts, primaries, secondaries, tertials and tail feathers were also fringed/tipped buff, with only the slightest hint of olive-green present, so minimal contrast in colour between the remiges/rectrices and the upperparts.
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| Plate 1 – Siberian Chiffchaff, Grimley, 22rd, 23rd April 2015. © Andy Warr |
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| Plate 2 – Siberian Chiffchaff, Grimley, 22rd April 2015. © Andy Warr |
Plate 3
The prominent supercilium was buff throughout and contrasted with the whitish eye-ring, plus lacked any trace of yellow, whilst the ear-coverts were rusty-buff and the bill predominantly dark, with orange-yellow restricted to the cutting edge. Due to the lack of yellow in the face, the yellow gap is particularly noticeable.
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| Plate 3 – Siberian Chiffchaff, Grimley, 22rd April 2015. © Andy Warr |
Underparts
Plates 4, 5 & 6
A strong buff colouration to the throat, breast, flanks, vent and thighs, whilst the belly and undertail-coverts were white. No trace of yellow could be detected on the underparts, plus appeared very limited on the lesser underwing-coverts, with just a hint of lemon-yellow on the latter and at the bend of the wing (see plate 6), though the extent of yellow on the axillaries was undetermined.
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| Plate 4 - Siberian Chiffchaff, Grimley, 22nd & 23rd April 2015. © Andy Warr |
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| Plate 5 – Siberian Chiffchaff, Grimley, 22rd April 2015. © Andy Warr |
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| Plate 6 – Siberian Chiffchaff, Grimley, 22rd April 2015. © Andy Warr |
Age, feather wear & moult
This individual has completed its pre-breeding moult and it’s body feathers are sleek and pristine. It has been aged as a first-winter, due to contrast between the new, darker and broader fringed inner greater-coverts and the shorter, paler and narrowly fringed juvenile outers, plus the even growth-bars across the outer tail feathers. The exposed primary tips and outer tail feathers were particularly worn and bleached to a dull pale brown and contracted with the fresher central tail feathers and tertials, all three of the latter appearing to be of the same age, so lacking contrast between any newly moulted inner tertials, if replaced during the pre-breeding moult. This suggesting that all the tertials and probably the two central pairs of tail feathers were replaced during the post-juvenile moult. An adult wouldn’t show any contrast in the greater-coverts, have uneven growth-bars in the tail and would be expected to possess a darker and glossier appearance to the primaries and outer tail feathers at this time of year. The pre-breeding moult is believed to be more extensive in adults, than first-winter birds.
Plate 7
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| Plate 7 – Siberian Chiffchaff, Grimley, 22rd April 2015. © Andy Warr |
Plate 8
A comparison of the remiges/rectrices to one of the Powick birds, which was considered an adults due to feather condition and the extensive pre-breeding moult.
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| Plate 8 – Siberian Chiffchaff, (top) Grimley, 22rd April 2015, (bottom) Powick STW, 14th March 2015 © Andy Warr |
Vocalisation
Song
Many recordings were obtained of the song and a sample
of these are featured below. Its song was pretty consistent throughout and no
song switching was heard from tristis
to collybita/abietinus, or vice
versa. Most, but not all the sequences recorded, included some note signatures
shared by or very similar to collybita/abietinus
and though these signatures are difficult to detect by ear on the recordings,
they a visible on the accompanying sonograms, conveying the appearance of a
reverse tick, and have been marked with a red line. Click on sonograms to enlarge.
Song sequence 1
Quite a few collybita/abietinus
type note signatures are present during the first half of this sequence, but are
absent towards the end. Duration 18 seconds.
For recording click here
For recording click here
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Sequence 1 sonogram
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Sequence 1 continued sonogram
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Song sequence 2
A shorter song, with two collybita/abietinus type signatures at the end. Duration 7 seconds.
For recordingclick here
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Sequence 2 sonogram
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Song sequence 3
For recordingclick here
An even spread of collybita/abietinus
type signatures. Duration 9.2 seconds.
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Sequence 3 sonogram
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Song sequence 4
A single collybita/abietinus type signature at the end of this song. Note the variation in structure of this note, compared to the other collybita/abietinus type signatures, distinctly rising at the start, then falling sharply before rising again, resulting in a very close start and end frequency of the complete note. Duration 11.7 seconds.
For recording click here
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Sequence 4 sonogram
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Song sequence 5
No collybita/abietinus type signature throughout. Duration 6 seconds.
For recording click here
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Sequence 5 sonogram
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Song sequence 6
A very short burst of song, again lacking any collybita/abietinus type signature. Duration 3.2 seconds.
For recording click here
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Sequence 6 sonogram
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This was by far the longest song sequence recorded, lasting for 46 seconds. Parts which included the collybita/abietinus type signature appeared ordered in distinct phases, forming a reasonably consistent pattern in both timing and duration. Consequently, there appeared to be an ordered structure to the song.
The timing and length of these phases were as follows.
Signature present – 10.8 seconds from start of sequence
Signature absent – 8.4 seconds
Signature present – 9.2 seconds
Signature absent – 8.8 seconds
Signature present – 8.2 seconds to end of sequence
This anomaly appeared consistent throughout all the longer song sequences recorded, including song sequence 1, where this signature was present for the first 10.3 seconds, then absent for the remaining 7.3 seconds of the song.
For recording click here
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Sequence 7 sonogram
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Sequence 7 continued sonogram
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Sequence 7 continued sonogram
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Sequence 7 continued sonogram
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Enlarged examples of the collybita/abietinus type, reverse tick signatures, with variations at the start of each note, the first, slightly bulbous, but dropping from the start, the second with a slight rise before falling (the two latter signatures being present in collybita/abietinus song) and the third a sharp rise before dropping, with the start at a lower frequency than the end of the complete note (a toppled Z). A true collybita/abietinus song, appears to lack this sharp rise at the start of the note signature, but is very similar to an alternative 'sweeoo' call delivered by collybita. See: click here
Recordings were selected from the bird sound website Xeno-canto, of individuals over 250miles east of the Ural Mountains, which mark the eastern boundary for abietinus, during the period late May, to the end of June, so presumably territorial males, rather than passage birds, which may be heading to their breeding grounds west of the Urals.
Seven, of the nine recordings found, contained collybita/abietinus type, or similar note signatures within the song and these are featured below in sonogram form, plus the date and a link to each recording has been included. Also one recording came from within and the other six outside the proposed range for ‘fulvescens’.
In addition, another recording was analysed from the tristis breeding range in Kazakhstan in early May, so potentially a territorial male, but a passage migrant couldn’t entirely be ruled out.
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This map
marks the approximate location and the Xeno-canto code for each recording
analysed
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Sonograms were produced for the entirety of each recording, then the best sequences selected for each bird, so most, but not all will appear the same as the sonograms featured on Xeno-canto, which portray the first song sequence from each recording.
Song sequence from
XC36357.
Shapsha, near Khanty-Mansiysk, Russian Federation, on
15th June. XC36357 click here
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XC36357 sonogram
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Song sequence from XC148826.
Berdsk, Russian Federation, on 21st June.XC148826 click here
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XC148826 sonogram
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Song sequence from
XC148827.
Berdsk, Russian Federation, on 21st June.XC148827 click here
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XC148827 sonogram
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Song sequence from XC148803.
Ongudaysky District, near Gorno-Altaysk, Russian Federation, 29th June.XC148803 click here
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XC148803 sonogram
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Song sequence from XC148804.
Ongudaysky District, near Gorno-Altaysk, Russian Federation, 29th June.XC148804 click here
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XC148804 sonogram
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XC162561 sonogram
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Song sequence from XC144519.
Turochaksky District, near Gorno-Altaysk, Russian Frederation, 16th June.
The toppled Z note signature is present throughout this sequence, an identical signature
to the one noted in song sequence 4 of the Grimley bird.
XC144519 click here
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XC144519 sonogram
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Song sequence from XC120396
Dzhukey, Kazakhstan, 6th May.
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XC120396 sequence 1 sonogram
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XC120396 sequence 2 sonogram
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XC120396 sequence 3 sonogram
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XC120396 sequence 4 sonogram
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XC120396 sequence 5 sonogram
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Enlarged signatures
Unfortunately, there were no recording on Xeno-canto of birds from the eastern breeding range of tristis.
Call
This individual rarely called, but two distinct notes
were recorded, the first a classic tristis,
even pitch monosyllabic ‘peet’ and
the second, a very quiet, rising disyllabic ‘hweet’.
Call 1
The classic tristis
‘peet’ call was heard on at least
three occasions.For recording click here Taken from a video recording by Brian Stretch, the call being right at the start of the recording.
Call 2
The ‘hweet’ call was heard on at least four occasions and ranged from 2.8 kHz – 4.6 kHz.
For recording
Note how similar in appearance the ‘hweet’ call signature is to notes included within the song. This may be one explanation for why calls sometimes deviate from the classic tristis ‘peet’.
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‘peet’ call
sonogram
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The ‘hweet’ call was heard on at least four occasions and ranged from 2.8 kHz – 4.6 kHz.
For recording
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‘hweet’ call
sonogram
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Note how similar in appearance the ‘hweet’ call signature is to notes included within the song. This may be one explanation for why calls sometimes deviate from the classic tristis ‘peet’.
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Sonogram of the ‘hweet’
call compared to a note signature within tristis song
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Conclusion by the author
On plumage, the Grimley bird appears about as good as
it gets for classic tristis and
whilst its song included note signatures similar to collybita/abietinus, this is matched by recordings of tristis at least as far east as the
central breeding belt and beyond the recognised limits of ‘fulvescens’, so consider it inappropriate to describe this
particular individual as a ‘mixed singer’. Based on the aforementioned, I conclude
that this was a thoroughbred Siberian Chiffchaff, which in turn, shows that
call can deviate from the so-called classic tristis
‘peet’. Acknowledgements
Many thanks to Alan Dean for his input and advise during the production of this article.
Written and compiled by Andy Warr.
