Eastern Lesser Whitethroats at Skagen

During the last weeks of October two Lesser Whitethroats of the Eastern types (S. curruca blythi/halimodendri) were caught and ringed at Skagen Bird Observatory. They arrived together with Siberian Chiffchaffs (P. collybita tristis) that also turned up in the area in the same period with six individuals caught between the 17th – 22nd October. In this article I’ll present the documentation and discuss the cases of the two records before we at a later point get the results of the DNA-analysis. The Identification of the different taxa within the Lesser Whitethroat complex has been a challenging matter for years. But hopefully by time we will get a better insight of their occurrence and identification by the increasing numbers of well documented birds in Western Europe and with more knowledge from their breeding and winter grounds.

On 20th  October 2019, a 1cy. eastern type Lesser Whitethroat (ssp. blythi/halimodendri) was caught while ringing at Kabeltromlekrattet (Grenen, Skagen). The bird was caught around 10:35 by Christian Stolz, Judith Kloibhofer, Koen Stork, Laia Soler Iglesias and Simon S. Christiansen and hereafter it was ringed. Age by juvenile tail, PC, Alula, grey eye colour and non-ossified scull. Pictures were taken as well as a few feathers where collected for DNA analysis. A description, full measurements of the bird are included further down. This individual did’nt call.

On 22nd October 2019, another 1cy. eastern type Lesser Whitethroat (ssp. blythi/halimodendri) was caught and ringed at the same place around 08:15 by the same people. Age by juvenile outermost GC, PC, Alula, tail and by eye colour. Again, pictures were taken and feathers collected. This bird was later also found in the field and the observers managed to record the call of the bird. One day after, the bird was recaptured. A description, brief analysis of the calls and full measurements of the bird are included.

How should an eastern bird look like?

An eastern bird (ssp. blythi/halimodendri) looks more brownish than ‘our’ Lesser Whitethroats (ssp. curruca) in general, but especially on the head. curruca has a greyish head with an obvious border in the hindneck between grey head and brown back. In eastern taxa the brown from the back is extending onto the head and there is no border between grey and brown. It is only a slight transition from grey to brown. In some birds, even the whole head is brownish rather than greyish (such as our second bird).
There are differences in tail pattern as well. Eastern birds have more white in the tail, but this feature has to be used with caution as it is only referring to first-year birds, adult curruca can have a similar pattern as first-year birds from eastern taxa. The pattern on T6 is most important, first-year birds of  curruca always have a T6 with some dark coloration along the shaft of the feather. Also, the feather is mostly not pure white, but more buffish white. In first-year eastern birds T6 is pure white with only a dark wedge visible on the inner web, there’s no dark coloration along the shaft of the feather. In addition to this, eastern taxa have pale tips to T5 and in many birds also T4. In curruca, this is lacking in most birds.
There’s another feature: the wing formula. This one is mostly useable in the hand though. In eastern subspecies P2 is shorter than in curruca. According to Cramp et al., 1992 there are no birds of ssp. curruca that show a P2 that equals P7 or is even shorter (n=147). In this sample only two birds show a P2 that falls between P6-7, versus 73 birds of eastern taxa (n=127). If the P2 is longer than this, it doesn’t exclude eastern subspecies (only if P2 equals P5) but it can’t be used as identification key.

Distinguishing halimodendri and blythi from each other is virtually impossible for sure without DNA as it is right now. However, there are a few clues. halimodendri tends to be more sandy brown, and with limited grey in the head. This subspecies also tends to have a more rounded wing with a broader and more blunt wingtip, shorter primary projection and shorter P2 than in blythi. Tail pattern is mostly the same, on average halimodendri has a little more white in the tail with obvious pale tips on T4-5 as well. But this is not really a useful clue since there’s very much overlap. The distribution of blythi is not known well, but it probably has a very large distribution in the northern part of Asia. The southern populations of blythi are bordering in to halimodendri in Central Asia while the Western part of the population are some where bordering in to curruca (Olsson 2013). We can therefore probably expect that blythi from the Western part of their normal distribution can resemble curruca while blythi in the Southern parts resemble halimodendri more.

Bird one, 20 October 2019

Eastern Lesser whitethroat, Skagen, 20. october 2019. Photo: Skagen Fuglestation
 

Description

Size and structure as nominate Lesser Whitethroat Sylvia curruca curruca in general. The bird gave the impression that it had a more rounded wing. Wing formula different from typical curruca with P2 = P7 (or even falls between P7-8 according to measurements) and wingtip formed by P3, P4 and P5. P3-4-5 emarginated.

Eastern Lesser Witethroat, Skagen, 20. october 2019. Photo: Skagen Fuglestation

Head greyish and contrasting with white throat and sideneck, but brown from the back extending far up on the nape (not all the way to crown). Crown most grey part (but not pure grey) of head, forehead slightly browner as well as hindneck. Lores dark grey. Ear coverts brownish, darker than surroundings and thus forming a mask. Feathers above the eye somewhat lighter grey, hinting to a faint supercilium. Lower half of eye-ring conspicuously white, upper half greyish and not contrasting with rest of the head.

Eastern Lesser Whitethroat, Skagen, 20. october 2019. Photo: Skagen Fuglestation

Upperparts plain sandy brown, low contrast. Only longest uppertail coverts slightly darker than rest of upperparts.

Upperparts of eastern lesser whitethroat in sunlight, Skagen 20. october 2019. Photo: Skagen Fuglestation

Upperparts of eastern lesser whitethroat in shade, Skagen, 20. october 2019. Photo: Skagen Fuglestation
  

Underparts whitish. Undertail coverts, belly and throat pure white. Flanks and side-breast more brownish white. Transition from pure to brownish white is gradually, low contrast. Underwing coverts whitish, longest underwing coverts with a brownish tinge.

Eastern lesser whitethroat, Skagen, 20. october 2019. Photo: Skagen Fuglestation

Wing brown, with a whitish wing panel formed by whitish fringes of inner secondaries and tertials. All feather groups with dark centres and sandy brown fringes. Secondaries, primaries, primary coverts, outer alula and maybe longest tertial are juvenile feathers. The rest are moulted and thus post-juvenile.

Eastern lesser whitethroat, Skagen, 20. october 2019. Photo: Skagen Fuglestation

Eastern lesser whitethroat, Skagen, 20. october 2019. Photo: Skagen Fuglestation
          

The tail is difficult to judge since there are four tail feathers missing. T6 shows extensive white, there is a dark wedge on the inner web which is not extending to, or close to, the top. The rest of the feather is white. The two middle tail feathers (T1) are more brownish, rather than the blackish-brown colour of the other tail feathers (except T6). About the rest of the feathers, with the bird in the hand we could not figure out which feathers they exactly were. We suspect that on the left side (bird’s perspective) of the tail T2 and T3 are missing. This would mean that T5 shows a small, pale wedge on the top of the feather and T4 shows only faintly pale tip.

Eastern lesser whitethroat, Skagen, 20. october 2019. Photo: Skagen Fuglestation

Legs grey, with pale soles. Nails also grey, somewhat darker than feet.

Bill mostly dark, base of lower mandible blue-grey in colour.

Iris olive-grey, black pupil.

 

Biometrics

Weight: 10,5 g
Fat: 2
Wing length: 65,4 mm
Tail length: 58 mm
Absolute primary projection: 10 mm
Length of emargination (wingtip to the start of the emargination) on P3: 20,5 mm
Length of emargination (wingtip to the start of the emargination) on P4: 14,5 mm
Length of emargination (wingtip to the start of the emargination) on P5: 12 mm

Wing shape relative to wing point (distance wingtip to tip primary)
P2: -4,3mm
P3-4-5: wingtip
P6: -2 mm
P7: - 4 mm
P8: -5 mm
P9: -6 mm
P10: -8 mm

Tail/wing ratio: 88.7

 

Discussion

This bird matches one of the three criteria very well: the wing formula. In this bird P2 equals P7. This alone should exclude curruca. About the other criteria, the head could have been more brownish. This bird still has a grey crown, but the sandy brown colour from the back is extending far up the nape, which is good for an eastern bird. The tail pattern is difficult to judge, but at least the pattern on T6 looks good with extensive and pure white on the feather and only a dark wedge on the inner web. The wing formula points to halimodendri rather than blythi. On the contrary, one would maybe expect a more brown head and even more extensive white on T6 for a typical bird of ssp halimodendri.  Another Danish record of an individual from Anholt in 2012 showed a wing formula and coloration favouring halimodendri. But the result from the subsequent DNA-analysis identified it as a blythi. With that in mind a guess on the taxa is difficult but I would still put my money on halimodendri to be the outcome of the DNA analysis on our bird since we expect that in general most birds with a similar appearance would be halimodendri.

 

 

Bird two, 22 October 2019

Eastern lesser whitethroat, Skagen, 22. october 2019. Photo: Skagen Fuglestation

Description

Size and structure as nominate Lesser Whitethroat Sylvia curruca curruca in general, small Sylvia warbler with long tail and slender body. The impression of a more rounded wing was mostly lacking on this bird, probably because the P2 on this bird is longer than on bird 1. The wing formula is indeed different from bird 1 with P2 falling between P6/7 (closer to P6, corresponding with measurements). The wingtip is less broad than in bird 1 with only P3-4 forming the wingtip instead of P3-4-5. P3-4-5 emarginated.

Eastern lesser whitethroat, Skagen, 22. october 2019. Photo: Skagen Fuglestation

Head mostly brownish with a grey tinge rather than greyish with a brownish tinge. Head strongly contrasting with white throat, also contrasting (but less distinct) with pale sideneck. Brown back extending far up on the nape, on the crown the grey tinge is well visible, as well as on the forehead. Feathers above the eye are the most greyish part of the head. Few feathers just above and in front of the eye are more light of colour, hinting to a small supercilium. Lores dark grey. Ear coverts dark brown, forming a contrasting dark ‘mask’ on the head. Lower half of the eyering is pure white and contrasting with the rest of the head. The sides of the eyering are dark and the upper half is brownish, not contrasting with rest of head.

Eastern lesser whitethroat, Skagen, 22. october 2019. Photo: Skagen Fuglestation

Eastern lesser whitethroat, Skagen, 22. october 2019. Photo: Skagen Fuglestation

Upperparts plain light brown without contrast. Uppertail coverts slightly darker than rest of upperparts. In comparison with bird 1, more brown in colour.

Eastern lesser whitethroat, Skagen, 22. october 2019. Photo: Skagen Fuglestation

Underparts dirty white, with a brownish tinge. Throat is pure white. Undertail coverts and central belly are dirty white, but brownish tinge less prominent than most of the underparts. Flanks and underwing coverts dirty white with an obvious brownish tinge. In comparison with bird 1, this bird has more brownish underparts.

Eastern lesser whitethroat, Skagen, 22. october 2019. Photo: Skagen Fuglestation

Wing brown, dark alula contrasting with rest of wing. Low contrast in rest of wing. All feather groups with dark centres and slightly lighter, brown fringes. No wing panel, although pale edge of longest tertial is obvious and hinting to the impression of a wing panel. Secondaries, primaries, alula carpal covert and maybe tertials are juvenile feathers, the rest are post-juvenile.

Eastern lesser whitethroat, Skagen, 22. october 2019. Photo: Skagen Fuglestation

Eastern lesser whitethroat, Skagen, 22. october 2019. Photo: Skagen Fuglestation

The tail is mostly blackish-brown with T1 showing a sandy brown colour more similar to the colour on the upperparts. T6 is mostly white with only limited dark coloration on the inner web. T5 and T4 show pale coloration as well. T5 has a buffy tip which slightly emerges into the blackish-brown colour of the rest of the feather. T4 has a similar pattern, but even less obvious, the tip is only slightly lighter in colour and the light coloration is restricted to the inner web of the feather.

Eastern lesser whitethroat, Skagen, 22. october 2019. Photo: Skagen Fuglestation

Eastern lesser whitethroat, Skagen, 22. october 2019. Photo: Skagen Fuglestation
 

Legs grey, with pale soles. Nails dark grey.

Bill mostly pale, blue-grey base to lower mandible. Grey base to upper mandible. Tip of the bill dark.

Iris olive-grey.

 

Biometrics

Weight: 11,8 g
Fat: 4
Wing length: 68,2 mm
Tail length: 58,5 mm
Bill to feathering: 13 mm
Absolute primary projection: 13,8 mm
Length of emargination (wingtip to the start of the emargination) on P3: 21 mm
Length of emargination (wingtip to the start of the emargination) on P4: 15 mm
Length of emargination (wingtip to the start of the emargination) on P5: 12 mm
Distance between tip of first primary and tip of primary coverts: 5 mm longer

Wing shape relative to wing point (distance wingtip to tip primary)
P2: -4 mm
P3-4: wingtip
P5: -1 mm
P6: -3 mm
P7: - 6 mm
P8: -8 mm
P9: -9 mm
P10: -10,5 mm

Tail/wing ratio: 85,8

 

Calls of the bird

The bird was found in the field later that morning and could be seen well. It was calling frequently and Simon managed to record it. The bird gave only ‘check’-calls and not the Tit-like rattling call typical of halimodendri. Ssp. curruca tends to give more dry (‘teck’ rather than ‘check’) calls than eastern subspecies. The calls of this bird are ‘check’-calls rather than ‘teck’-calls. However, there is much overlap in the calls.

Spectogram of the call. Skagen 22. october 2019.

Sound recording

 

Discussion

This bird matches all three criteria. Wing formula is not ruling out curruca, but is better for one of the eastern subspecies. The head is really brown, it’s brown with a greyish tinge rather than grey with a brownish tinge. Also tail pattern is spot on with extensive, pure white on T6 and pale tips on T4-5. The wing formula of this bird is more like a wing formula that one would expect for blythi rather than halimodendri with the wingtip formed by P3-4 and a somewhat longer P2 in comparison with bird one. Also, the primary projection is rather long which is better for blythi. Tail pattern is probably better for blythi as well, with only slight pale tips on T4-5. One would maybe expect them to be more conspicuous on typical halimodendri. But the best clue is probably the call, most birds of ssp halimodendri would give a Tit-like rattling call and not this kind of ‘check’-call. On the contrary, this bird is really brown! The head is brown with only a greyish tinge, there’s no pure grey feathers on this bird it seems. This fact might seem to be favouring halimodendri over blythi. However, with the call and it’s wing formula and tail pattern I’d put my money on blythi being the outcome of the DNA analysis.

 

Status of eastern type birds in Denmark

To date there are five accepted records of eastern type Lesser Whitethroats in Denmark. Two birds have been accepted as ssp. halimodendri, two birds as ssp. blythi (all also documented on DNA analysis) and one bird ringed in 1992 is labelled as ssp. halimodendri/minula but this was accepted before the current knowledge of the different taxa and their distribution where we now a days expect ssp. minula to be “extralimital” in Europe. Today this record would probably fall in the category of ‘Eastern Lesser Whitethroat’ ssp. halimodendri/blythi. Full records are shown below:

20/10/1992 – Lesser Whitethroat ssp halimodendri/minula at at Blåvands Huk, RB (1cy)
05 - 09/11/2011 – Lesser Whitethroat ssp halimodendri at Grønningen, Blåvand, RB (1cy)
20/10/2012 – Lesser Whitethroat ssp blythi at Totten, Anholt, ÅH (1cy)
27/10/2016 – Lesser Whitethroat ssp blythi at Gedser Odde, LF (1cy)
18/10/2018 – Lesser Whitethroat ssp halimodendri on Christiansø, B (1cy)

Furthermore there’s one former record of an individual from Skagen that’s still pending:

06/11/2013 – 01/01/2014 Lesser Whitethroat ssp. halimodendri ringed at Grenen, Skagen, NJ (1cy), where the DNA-analysis fall in to “clade 2b” of ‘halimodendri’ in the phylogenetic tree made by Olsson (2013). You can read more about the taxa and genetic analysis of Lesser Whitethroats in the paper of Olsson et al. (2013).

However, the real number of eastern type birds is much higher since every autumn multiple late, brown Lesser Whitethroats are seen in Denmark. These birds are probably almost all from eastern origin. The situation in the rest of north-western Europe is the same. In recent years, sightings of this late, brown birds have increased. This is probably also caused by more awareness of the occurrence of eastern taxa. Another factor could be that eastern type birds actually has increased in numbers, as is the case with Yellow-browed Warbler Phylloscopus inornatus for example.

 

Text & Photos by Koen Stork, Skagen Bird Observatory

Comments by Simon S. Christiansen, Skagen Bird Observatory

 

 

References:

Cramp et al., 1992. Handbook of the Birds of Europe, the Middle East and North Africa. Volume VI Warblers.

Demongin, 2016. Identification Guide to Birds in the Hand.

Olsson et al., 2013. New insights into the intricate taxonomy and phylogeny of the Sylvia curruca complex.

 

Shirihai, Gargallo & Helbig, 2001. Sylvia Warblers. Identification, taxonomy and phylogeny of the genus Sylvia.

Websites: Olsen, 2012 :“Siberian Lesser Whitethroat in Denmark”: http://birdsdk.blogspot.com/2012/10/central-asian-desert-lesser-whitethroat.html

 

Koenraad Stork

Koen Stork is a young and keen Birder from the Island Texel in the Netherlands. A place that has given him great opportunities to study the migratory birds in his free time since childhood. In this autumn Koen was chosen to take part in the exchange program ”The Scandinavian Triple” working for three months in total on three different Bird Observatory’s: Ottenby (Sweden), Lista (Norway) and then Skagen (Denmark) here in October.

Koenraad Stork in the field.