Martin Garner and David Cooper
The slightly confusing mix of characters visible in photos including active wing moult leading to some head scratching. Only Willow Warbler and Arctic Warbler are normally in active pre-breeding moult and when the calls were finally captured it was sorted- an Arctic Warbler. I think the general assumption too was that it was a Eurasian bird- of the nominate form ‘borealis’, least that was in MG’s head.
See the Original Post asking for help with ID (before sound recorded)
More images were added HERE
Then after sound recording the ID conclusion was written up HERE the Bermuda Arctic Warbler – but which taxon and from where?
The call never sounded right. That’s to say that one of the best places to see Arctic Warbler this side of the pond in autumn is Shetland. And they always or nearly so give a single dipper-like slightly raspy call ‘dzik’. A single note. The Bermuda Warbler often/ most frequently gave a double note. I checked with Roger Riddington and Paul Harvey who have seen lots of Arctic Warblers. Invariably only uttering single notes bar one late bird 2 autumns ago which occasionally gave a double note. Sonagram of Bermuda Arctic Warbler giving both single and double notes Sonagram of Bermuda Arctic Warbler giving typical double notes
With David Cooper, we began to compare the Bermuda bird with other ‘Arctic Warbler’ taxa. We started with the 3 way split including borealis, examinandus and xanthodryas. See the paper explaining the split. It sounded closest to examinandus, but not quite right (better heard than looking at double note sonogram.). The Bermuda bird was then compared with calls of the Alaskan form kennicotti. Bingo/ snap. At least we think so.
Have a listen look at sonograms, consider the very late extra yellow visible on the Bermuda bird.
Listen to: Kamchatka Leaf Warbler examinandus, Arctic Warbler borealis and Japanese Leaf Warbler xanthodryas >>> HERE <<<
Listen to: Alaskan kennicotti >>> HERE <<<
Listen to: the Bermuda Arctic warbler >>> HERE <<<
Oh and if kennicotti can reach Bermuda– a shorter distance, great circle route could take kennicotti to… Shetland, or the Outer Hebrides or pretty much anywhere in Britain. #just saying.
Alaskan kennicotti and taxonomy?
One might further ask the question whether the taxonomy of Kennicott’s Warbler... kennicotti needs a re-appraisal…
The Bermuda Arctic Warbler– best fit kennicotti... kennicotti Arctic Warbler kennicotti Arctic Warbler. Sonagram and sound virtually identical to Bermuda phyllosc. kennicotti Arctic Warbler- some recordings contain single notes too
Akihiro Sakuma from Japan kindly commented as follows::
Oh! It’s very difficult to identify what ‘ Arctic Warbler ‘.
But for me it seems to be ‘kennicotti ‘.
‘borealis‘ upperparts are more dark green colour and underparts dusky
without yellowish, and also some streaks on its breast.
But this ‘Arctic Warbler’ s underparts yellowish and without streaks on its
‘examinudus’ also has yellowish underparts but is not smart proportion like
this ‘Arctic Warbler’
And this ‘Arctic Warbler’ call is not like ‘examinandus’ ( Kamchatka Leaf
So I think this Arctic Warbler ‘ is ‘kennicotti ‘, and as its
underparts and supercilium are yellowish, it seems to be 1st winter .