onsdag den 31. oktober 2012

Siberian Lesser Whitethroat (blythi) in Denmark

UPDATE: The result of the genetic analysis confirms what we had always thought - that this was a Central Asian Lesser Whitethroat somewhere on the blythi—halimodendri spectrum and based on cytokrom b the bird falls into the blythi clade as defined in the recent paper by Olsson et al (2013).


On Saturday the 20 October 2012 I found a Lesser Whitethroat which was seen briefly in the garden at Fyrgården near Totten on the easternmost tip of the island Anholt. It was striking and called for immediate attention due to its short primary projection; fine and short bill; warm underparts suffused with peachy-buff and less contrasting against the upperparts compared to a typical curruca; and sandy brown upperparts with a warm hue extending onto the head.

The sun was about to set, so my mist-net in the garden were opened right away and by the use of playback the bird was easily caught within 20 minutes. I immediately checked the wing-formula and noticed a very rounded wing, with a short P2 falling almost even with P8 and P3-P4-P5 of equal length and creating the wing tip. As the sun had just gone down during the netting process, the bird was taken to the house for carefully examination and ringed (9R 88 331) before it was left for the night in a bag. At first daylight the following day the bird was released in the garden from where it quickly moved on to never be seen again.

As the identification of vagrant Lesser Whitethroat in Europe is highly complex a small blood sample and an outermost tail-feather, a central secondary and a few coverts were sampled for genetic analysis.

Field characteristics: • Brown on nape • Lack of contrast between crown and mantle • White throat contrasting with peachy or buffy flanks and breast • Lack of clear dark mask • Lores paler than usual • Sandy or pale to mid-brown upperparts • Short-winged/long-tailed jizz.

Throat white, breast dull buffish-white, sides of breast and flanks pinkish-buff.

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 five greater secondary coverts with gingery-reddish fringes, inner five darker and longer. The large alula-feather dark sepia, rather contrasting.

Mantle and rump rather pale sand-brown with a slight reddish tone. Hind-crown grey admixed with the same colour as the mantle. Legs dark blue-grey.

P3-P4-P5 create wingtip

Short primary projection with only six primaries visible beyond longest tertial.

Plumage tones on the upperparts were sandy / pale in good light, but appeared a more rich buff-brown in shadow. Perhaps most importantly, there was very little contrast anywhere except the forecrown and ear coverts. Note how the buff-brown tones extend right up the nape and onto the crown (areas that would be greyer on western Lesserthroat). At most angles the ear coverts also looked similar in tone to the crown and mantle, with darker grey tones only appearing at certain postures.

The bird was aged as a first-year. It had a moult limit between five outer juvenile greater coverts with warm sand-coloured fringes and five inner, which were longer, less worn, darker brown and with less distinct pale fringes.

I've occasionally seen similar mantle tones to this bird on 'standard' autumn Lesserthroats, but they have always been combined with both grey crown and gleaming white underparts. This bird had distinctly sandy-buff tones to the entire underparts away from the throat.

Biometrics: Wing: 64.0 mm; Tail: 58.2 mm; Tail/wing ratio (x100): 90.9; Bill to skull: 12.2 mm.

P2 fall between pp 7 & 8 and almost completely on level with p8.

Emarginated pp 3, 4 & 5.

Tail (from above): Dark grey except for the central pair, which was brownish. The outermost tail-feathers had a juvenile pattern. The second outermost tail-feathers were only narrowly fringed white.

Under tail-coverts white with a faint buff tone.

Ear-coverts brown and grey, only slightly darker than the crow. Iris pale grey-brown with a hint of warmer brown tinge and with slightly paler and greyer upper half. 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.

2 kommentarer:

George Sangster sagde ...

Has the DNA evidence for this bird being a blythi been published (in print)? If so, do you have a link?

Kent Olsen sagde ...

the DNA result has not yet been published, but we are preparing a paper with DNA results from two records of blythi and two records of halimodendri from Denmark. The DNA analysis of the current individual was conducted by Urban Olsson who has the results