Could this become the first spring record of Siberian Lesser Whitethroat (Sylvia curruca blythi) documented by DNA in Denmark?

UPDATE: The result of the genetic analysis concludes that it had mitochondrial DNA belonging to Sylvia curruca curruca. As the difference in nuclear DNA between curruca and blyth is very little, it is however difficult to exclude a mixed origin. Nevertheless, we can say with confidence that the bird falls into the curruca clade as defined in the recent paper by Olsson et al (2013) and moreover, at least its mother was a nominate curruca.

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This Lesser Whitethroat was singing for three days before it apparently moved on. As the song was very characteristic and its plumage distinct, the possibility that it was in fact a Siberian Lesser Whitethroat Sylvia curruca blythi was emidiatly considered. When comparing its song with recordings of blythi from Russia, Mongolia and Kazakhstan which are available on Xeno Canto and AVoCet, the resemblance was striking. Therefore the bird was mist netted yesterday on May 21, 2014 in order to secure an in hand inspection, a wide range of biometrics and a feather sample for future DNA analysis.

Urban Olsson has agreed to analyses the feather and we wait to see if this is the first spring record of a Siberian Lesser Whitethroat in Denmark. Meanwhile is worth to consider the recent insights into the intricate taxonomy and phylogeny of the Sylvia curruca complex where they conclude that according 'to the mitochondrial gene tree, there is a basal dichotomy, with the taxa althaea, blythi, halimodendri and margelanica being part of one clade, well separated from a clade containing curruca and minula. Dating analysis suggests that a basal divergence separating curruca and minula from the other four taxa occurred between 4.2 and 7.2 mya; these two then diverged between 2.3 and 4.4 mya. The splits between the althaea, blythi, halimodendri and margelanica lineages is inferred to have occurred later, approximately between 1.0 and 2.5 mya'. Whether these clades should be treated as subspecies or species is in the future… but from a twitchers perspective one may want to play it safe.

Listen to the distinct song in these two recordings:



... and compare it to the songs in these two from Lake Baikal by Magnus Hellström:



... and this recording AV#9653, Mongolia from Avian Vocalizations Center (AVoCet). Occasionally, the Danish bird sang with curruca-like rattles mixed into the song, but this is also heard from bird recorded within blythi range such as in this recording from Kazakhstan:

Note that the white throat contrasts with the buffy flanks and breast.

Note the distinct mid-brown upperparts, including nape, tertials, uppertail coverts and upper tail.

Note that the uppertail coverts are grey in the normal curruca (left) whereas they are obviously more warm brownish in the possible blythi (right).

Note that the possible blythi (rigth) lacks a clear contrast between rear crown, neck, mantle and uppertail.

Note how the brown on nape penetrates further onto the crown on the possible blythi (rigth) than in the normal curruca (left). When handling the three different Lesser Whitethroats, the possible blythi stood out as having both a short tail and short primary projection relatively to the overall length of the bird. In direct comparison to the normal curruca (left) this short-handed and short-tailed JIZZ was striking.

Note that both the dark ear-coverts and the whitish supercilium are not as distinct in the possible blythi (left) than in the normal curruca (right).

Note that the centre of the central tail feathers are darker and in stronger contrast to the upperparts in the normal curruca (bottom), a contrast not present in the possible blythi (top). When handling the three different Lesser Whitethroats, the possible blythi stood out as having both a short tail and short primary projection relatively to the overall length of the bird. In direct comparison to the normal curruca (bottom) this short-handed and short-tailed JIZZ was striking.

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Note that it lack of clear dark mask and that the lores are paler than usual.

P2 fall almost completely on level with P6.

Here the wing is compared with the 'Siberian Lesser Whitethroat (Sylvia [curruca] blythi) found on Anholt in october 2012.

 

	blythi?	curruca	curruca	blythi	halimodendri
Locality	May 2014 Feldballe	May 2014 Feldballe	May 2014 Feldballe	October 2012 Anholt	November 2011 Blåvand
Metal ring no.	9L62761	9L62762	9L62763
Age & sex	2cy male	3cy+	2cy
Wing length (max)	63.7 mm	65.0 mm	67.3 mm	64.0 mm	59.0 mm
Tail length	55.1 mm			58.2 mm	55.0/56.0 mm
Tail/Wing ratio (x100)	86.4			90.9	94.1
Bill to skull length	10.4 mm			12.0 mm	11.0 mm
2nd P	= P6	= P5/P6	= P5/P6	= (P7)/P8	= P8
Wing tip	P3	P4	P4	P3-P4-P5	P3-P4-P5
Bill height (front nostrils)	2.9 mm
Bill height (rear nostrils)	3.3 mm				3.0. mm
Bill width (front nostrils)	2,75 mm
Bill width (rear nostrils)	3.3 mm				3.5 mm
Tarsus length	22.1 mm				19.0 mm
1st P > Alula	12.5 mm				12.0 mm
1st P > PC	5.4 mm				3.5 mm
Wing tip > longest tertial*	12.3 mm	14.2 mm	15.7 mm		11.0 mm

*In curruca this distance between the longest tertial and the tip of the longest primary is normally 13-17 mm.