Willow Warbler revisited

Hi Jim
It was a while ago now but I don't recall it being like other Willow Warblers.

Interesting at the time.

Russell

Interesting bird. Was the preliminary part of its song characteristic of a willow warbler before becoming a twitter?

Prompted by Phil Hyde to have another look at some photos I took back in May of 2006 ( see attached) of a pale Willow Warbler,
I searched the internet to see if there were any sub species of Willow Warbler that fitted my bird.
Back in 2006 I had only been birding for a few years and trying to identify anything down to sub species was out of the question.
I did think at the time though that this bird was different from any other Willow Warbler I had seen and left the photo on the LBC site album for anyone to comment.
No comments were made so I didn't think any more about it till today.
At the time I thought the bird looked slightly larger than a typical Willow Warbler, it seemed more confident being perched on top of a small bush, had a more robust appearance, an obvious well formed supercillium, but what struck me most of all was the very cold grey upper body and almost white undersides with the lack of any obvious yellow/green fringing to the feathers seen on most Willow Warblers. I noted at the time that "It's song was not like other Willow Warbler's songs, more like a short warble ending in a twitter." I know that description is not much to go on but it does show that the song was at least different.

There seems to be three main sub species of Willow Warbler:
1: "Phylloscopus trochilus trochilus", very common and widespread leaf warbler which breeds throughout northern and temperate Europe and Asia, from Ireland east to the Anadyr River basin in eastern Siberia. It is strongly migratory, with almost all of the population wintering in Sub-Saharan Africa.
2: "Phylloscopus trochilus acredula", Breeds northern Scandinavia east to western Siberia, winters central Africa.
3: "Phylloscopus trochilus yakutensis", Breeds eastern Siberia, winters eastern and southern Africa.

BBRC Quotes:
" Willow Warbler Phylloscopus trochilus

Willow Warbler comprises three subspecies – nominate trochilus from Britain, central Europe and southern Scandinavia, acredula (‘Northern Willow Warbler’) from northern Scandinavia, Russia and western Siberia and yakutensis (‘Siberian Willow Warbler’) from central and eastern Siberia. However, the subspecies are not well defined and there is extensive intergradation. Furthermore, variation is not linear, and birds showing the characters of one subspecies occur regularly within the range of another (Cramp et al. 1992).

Nominate trochilus is an abundant summer visitor and passage migrant to Britain, whilst acredula is a common pasage migrant, mainly to the east coast. The subspecies yakutensis is not on the British List but is a potential vagrant and birds showing its published characters have been noted in Britain.

The identification of yakutensis is problematic, however. This subspecies tends to be more grey-brown above and off-white below, with very little green and yellow in the plumage, but given the extensive intergradation with acredula and the appearance of yakutensis-like birds within the range of both acredula and nominate trochilus, it is not clear how a firm diagnosis can be made. Biometrics might be useful in some cases, yakutensis being on average longer-winged than the other subspecies.

Claims of potential yakutensis are welcomed if accompanied by detailed notes, good photographs and biometrics but a ringing recovery is probably necessary to secure its admission to the British List. (updated Dec 2017 AMS)."

At the very least I have learnt something today and hope this helps others look for the unusual in the common birds of Lincolnshire.

Russell