Thure Wikberg has been kind enough to add a couple of excellent sound recordings of the call of this bird, which sounded very unfamiliar for most listeners. Depending on which connection you have to the Internet you can choose among three sound files with basically the same content. If you want to get in contact with Thure, please send a note to birds@landsort.com.
Original recording including background sound (5.7 MB) 
Shorter version with background sound filtered (1.6 MB)
The same, in 8-bit mono (0.2 MB)
All pictures by Björn Anderson . You can watch more of his pictures here .
Comments on this bird here .
On 30th october 2000, Erik Wahlberg and Staffan Wieslander found a Lesser Whitethroat Sylvia curruca on Landsort, an island in the south Stockholm archipelago off the Swedish east coast. Weather conditions and observation circumstanses didn’t permit any further identification, but the extremely late date spoke in favour of some eastern race.
The bird in the field
During the following
days the bird was seen by a handful observers. It frequented a garden in the
village, sharing time between a thick Ivy Hedera helix on a rock wall, a high
Silver spruce Abies alba and thick bushes nearby, bushes of Yew Taxus baccata,
and trees of Sorb Sorbus sp. It was seen eating insects, preferrably large
flies, and berries. It frequently flew up to the Silver spruce and ascended
almost to the top, foraging and was frequently heard calling.
All agreed that
it had a strange jizz, different from normal Swedish nominate Lesser
Whitethroats (the race curruca). Compared with curruca, the body shape was less
compact, an effect of a proportionately longer tail and a more protruding head.
The colouration was different too: the upperparts appeared paler, sandy brown
with a slight red hue; the underparts were warmer, suffused with pink and buff,
less contrasting against the upperparts compared with curruca. In some angles it
was possible to see that the iris was pale, somewhat recalling a Desert Warbler
S. nana. The bill appeared long, but this was an effect of loss of feathers on
the throat and around the base of the bill. The call was something none of us
had ever heard from a Lesser Whitethroat: a rapid series of ’che’ or
’dze’-sounds: ’dze-ze-ze-ze-ze’, recalling Blue Tit or Tree Sparrow. On a tape
recording (made 24th november by Thure Wikberg) the number of syllables are
between 4 and 8. The tone was somewhat reminiscent of Reed Warbler. The typical
’tec’-call was never heard, though the bird responded to similar clicking sounds
from an Audobon bird call device.
On one occasion I saw the tail from below;
the outermost tail-feathers had a very interesting pattern with a lot of white,
recalling an adult curruca.
A mist-net was raised in the garden, by kind permission of the owner, Mr Björn Öberg, and the bird was easily caught. I immediately checked the wing-formula and noticed a very rounded wing, with four primaries falling within one millimetre. The bird was taken to the bird observatory, where it was ringed and carefully examined. An outermost tail-feather was sampled for DNA and isotope analysis.
THE BIRD IN THE HAND
Age
The bird was
aged as a first-year. The skull was not completely ossified; it was
approximately in stage ”C” according to Svensson (1992, p. 43), but the border
between pink and bone-white was diffuse. It had a moult limit betwen six outer
juvenile greater coverts with warm sand-coloured fringes and four inner, which
were longer, less worn, darker and more grey-brown and with less distinct pale
fringes.
Biometrics
Fat
score (0-9): 4. Body moult status: completed. Weight 11,0 g
Wing 63,5
mm
Tail 59 mm
Tail/wing ratio (X100) 92,9
Tarsus 19,7 mm (method fig.
18b in Svensson, 1992)
Bill to skull 12,6 mm
Bill to distal part of
nostrils 6,9 mm
Wing-formula
(primaries numbered ascendantly)
Emarginations and notches
Emarginated pp
3, 4 & 5
Notch on pp 2, 3 & 4, and faintly on 5
Notch on p2 =15,4
mm; on p3 =12,5 mm; on p4 =12,0 mm
Primaries in relation
to wingtip (WT)
P1 =32 mm; p2 =4 mm; p3 =0,4 mm; p4 =WT; p5 =WT; p6 =1 mm; p7
=3 mm; p8 =5 mm; p9 =6,7 mm; p10 =8,3 mm.
P2 fell between pp 7 & 8
Description
Upperparts:
Mantle
and rump rather pale sand-brown with a slight reddish tone. Upper tail-coverts
blueish-grey with narrow dark shaft-streaks and narrow sandy fringes.
Hind-crown grey admixed with the same colour as the mantle. Fore-crown and supercilium purer blue-grey, tending to almost whitish on the rear supercilium, creating a faint eyebrow behind the eye. A white narrow crescent under the eye (half eye-ring). Ear-coverts brown and grey, only slightly darker than the crown. A dark grey spot on the lores.
Underparts:
Throat
white, breast dull buffish-white, sides of breast and flanks pinkish-buff. Under
tail-coverts white with a faint buff tone. Belly white.
Wings:
Medium brown
flight-feathers, with slightly paler fringes. Primaries tipped buffish-white.
The longest tertial rather dark brown with indistinct narrow pale fringes; the
two shorter tertials pale sandy-brown, slightly darker around the shaft. Outer
six greater secondary coverts with gingery-reddish fringes, inner four darker
and longer, as described under Age. The large alula-feather dark sepia, rather
contrasting.
Tail (from
above):
Dark grey except for the central pair, which was brownish. The
outermost tail-feathers had a white pattern which was intermediate between adult
curruca and adult althaea according to the drawing on p. 198 in Svensson (1992).
The second outermost tail-feathers had small white tips and narrow whitish
margins, especially on the inner webs.
Bare parts:
Iris
pale grey-brown with a hint of warmer brown tinge and with slightly paler and
greyer upper half. Legs dark blue-grey. Bill with a rather pale, turqouise
green-blue patch on the mid part of the lower mandible and a dark tip. Upper
mandible blackish with pale bluish-grey cutting edges.
First thoughts
We could not determine which subspecies of Lesser Whitethroat we had trapped. Having no experience of the races in question, identification was difficult. At first, I ruled out curruca, blythi and also halimodendri, which according to available sources normally has a less rounded wing. The proportionatelly long tail pointed towards minula.
The
outermost tail-feathers had much more white than in first-year curruca, and the
limit between white and dark grey-brown was much more distinct; on the same
time, there was less white than in adults of the Central Asian races. However,
on the second occasion the bird was caught (see below!) a new feather had
started to grow, replacing the one I sampled, and this new one, or what was seen
of it, was much purer white and clearly of adult type. Furthermore, during the
last days of the bird’s stay, at the end of december, one observer, Svante
Åberg, noted ”a lot of pure white” on the left side of the tail when the bird
flew off.
The tail pattern indicated an eastern origin.
The second session
During November I corresponded with Lars Svensson, who on description believed the bird to be a halimodendri. He said that the best thing was if he could see the bird live, because photographs are often misleading regarding colour tones, and since the differences in plumage between the various races are subtler than many believe. On 25th November, Lars came to the island and the bird was once again easily caught.
When examining the bird in the hand, Lars stated that it was closest to halimodendri. This opinion was based on many specimens of this race handled in Khazakhstan. The difference between halimodendri and minula, however, can be very slight, both in measurements and in plumage, and judging from morphologic characters the two seem to be closely connected and are presumably intergrading in a large area in Turkmenistan and possibly Uzbekistan. Although the general plumage thus corresponded best with halimodendri, the wing of the Landsort bird was, as Lars pointed out, very rounded for a halimodendri, and p2 was untypically short (falling between pp 7 & 8) and, furthermore, the tail was proportionately long for that race; these characters all tended towards minula. The bill length was within the range of both halimodendri and minula; the wing length was in the lower range of halimodendri and the upper range of minula. The measurements compared with here are Lars Svensson’s own.
DNA
The base of the sampled tail-feather was sent to Urban Olsson, University of Gothenburg, for DNA analysis. The cytochrome b gene was sequenced and compared with sequences from specimens of the races curruca, halimodendri, minula and althaea. The Landsort bird turned out to be most closely related to, but yet clearly different from, Lars Svenssons specimens of halimodendri from Kazakhstan. Analysis of further populations is thus needed before a certain diagnosis can be made.
Final remarks
The
Lesser Whitethroat remained on the island during December, feeding in the
gardens along with Robins, Wrens and at least one Blackcap. This turned out to
be an extraordinarily mild December, but just before Christmas the temperature
fell and brought snow, forcing the birds to be more mobile.
Many birders were
able to make aqcuaintance with this interesting bird during it’s long stay, most
of them spontanuosly saying - whether scientifically correct or not - ’this is a
tick’.
It was last seen on 30th December.
Acknowledgments
I would like to thank these people: Lars Svensson, Stockholm; Urban Olsson, Falkenberg; Björn Öberg, Landsort; Björn Anderson, Uppsala; Thure Wikberg, Västerhaninge; Bertil Johansson, Stockholm; and everyone who participated in the work on Landsort Bird Station during the autumn 2000.
© Landsorts Bird Observatory. Updated 2002-12-01.