Hi all,
there have been one or two postings on the bill colour of Arctic on bird forum which have proved useful.
Was ear-marking this has something that should be shown around not specifically identifying it as such.
Think one would be hard pressed to find a photograph or even a written description of a known borealis without the tell-tale really pronounced, dark bill tip. The examples given are not IMO proven, borealis. John seems to find the OP as having an unmarked bill. Also yellow as is possibly present on the OP.l Do not think many will disagree that the moult of borealis, late July( suspended) and then sometimes as late as April, with the body moult mainly in Dec/Jan! Some may find the underpart colour of borealis noticeably different from all the others during this period. At least this can be tested in the field. Personally this why I believe the other posters have veered off towards TBW and PLW!
Firstly, regarding
borealis moult timing, you clearly didn't read post 4. All age classes undergo a head/body moult and including some retrices post breeding and prior to autumn migration. A complete pre-breeding moult takes place on winter-quarters (BWP). And this is what Wells has to say:
MOULT All age/sex classes moult head/body and some tail-feathers prior to arrival (BWP). No further moult has been reported among autumn passage migrants or in early winterers but, apparently all age classes moult again (fully?) in late winter. Primaries are replaced regular-descendently, and intensively (with up to 5 inner feathers in overlapping growth) as early as February. Most February-and all of March-dated birds handled were in moult, wing moult completing between mid-March and early April (p8-9, 9 or 8-10 on 1 April). T1 drops coincident with p6 or 7 and tail-moult at this season can also be intense (most feathers overlapping growth on 15 March:ZRC-NUS) to finish coincident with p10. Body moult continues longer with latest record (light moult of underparts) on 1 May (UMBRP)
So, they do not undergo a body moult as early as Dec/Jan-perhaps you'd care to provide a reference?
I sent the images to Phil Round and this is his reply:
The default arboreal Phyllosc in S Thailand, once you have excluded YBW and ECLW, especially in coastal woodland and mangroves, would have to be Arctic. I have little doubt that is what this is.
Phil
I have just contacted Phil to ask whether or not
borealis can show a completely pale lower mandible
i.e, lack a distal dark spot, and he came back to me with an image illustrating this within a matter of minutes! And before you ask, it was trapped and confirmed as
borealis (wing 61.5 & short p1: 2.3 <pc) including a sound recording, which 100% eliminates Kamchatka.
Grahame
P.S I would post the image if it were mine and if I knew how....you will just have to take my word for it. It seems they may not be that unusual.