The two Lesser Whitethroats were both curruca

The result of the genetic analysis on the two possible Siberian Lesser Whitethroats from Feldballe, May 21, 2014 and Anholt, June 1, 2014 confirms that they both had mitochondrial DNA belonging to Sylvia curruca curruca. As the difference in nuclear DNA between curruca and blythi is very little, it is however difficult to exclude a mixed origin. Nevertheless, we can say with confidence that the two birds fall into the curruca clade as defined in the recent paper by Olsson et al (2013) and moreover, say that at least its mother was a nominate curruca.

They were both originally thought to be possible blythi based on their distinct songs. However, when caught their wing formula did not differ significantly from curruca as much as the wing formula on the DNA-confirmed blythi from Anholt, October 20, 2012 did.

Below are some photos of the bird from Feldballe:

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

It is the bird to the right.

P2 falls between P5 and P6 (almost on level with P6).

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

Is this another Siberian Lesser Whitethroat?

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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During mist netting at Totten on the eastern most tip of Anholt we caught surprisingly many 2cy Lesser Whitethroats. Because of the possible blythi from the week before I paid extra attention to their song, but all the types we heard were of the western curruca type.

Early morning on June 1, 2014 something quite different was suddenly heard singing with a distinct song. As my sound recording equipment was already running nearby in order to get migrant calls, I just grabbed it, and went for the song. Luckily the bird continued to sing for several minutes at close range and showed quite well in the early morning light. As the song was very characteristic and its plumage distinct, the possibility that is was in fact a Siberian Lesser Whitethroat Sylvia curruca blythi was emidiatly considered. The bird had rather faded brownish upperparts and some smudging on the underparts and was thus quite different from most of the other Lesser Whitethroats seen.

Luckily, it moved into some trees near one of my mist nets and with less than one minute of playback, it dived straight into the net. A wide range of biometric measures were recorded and a feather sample secured for future DNA analysis before it was released again.

The bird was heard singing more than fifty times and always with the same rapid cycling song. Listen to the two recordings below to hear how distinct it was. Could this cycling song without the classic curruca rattles be unique for Siberian Lesser Whitethroat and thus allow us to make safe field identifications in spring just like in Siberian Chiffchaff?




The two recordings above are from Anholt, whereas I made the two below in Feldballe. Listen to the similarities between the two birds:



... and compare the two birds in the four recordings above with the songs in these two below from Lake Baikal by Magnus Hellström:

	21/5-2014	1/6-2014
	Feldballe	Anholt
	blythi?	blythi?
Metal ring no.	9L62761	BX06856
Age & sex	2cy male	2cy male
Wing length (max)	63.7 mm	65.0 mm
Tail length	55.1 mm	56.85 mm
Tail/Wing ratio (x100)	86.4	87.5
Bill to skull length	10.4 mm	10.23 mm
2nd P	= P6	= P6
Wing tip	P3	P3-P4
Bill height (front nostrils)	2.9 mm	2.81
Bill height (rear nostrils)	3.3 mm	3.14
Bill width (front nostrils)	2,75 mm	3.15 mm
Bill width (rear nostrils)	3.3 mm	4.59 mm
Tarsus length	22.1 mm	21.58
1st P > Alula	12.5 mm	12.15 mm
1st P > PC	5.4 mm	3.64 mm
Wing tip > longest tertial	12.3 mm	13.52 mm

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.