Thursday, 8 March 2012

Snow Bunting races

On our recent trip to Norfolk I managed to read a darvic (Yell H7) on a Snow Bunting within a flock of 50+ others and I promptly received feedback from Colin Carter of the East Norfolk Ringing Group. The bird was not ringed far away; in Kessingland, Suffolk but had moved back and forth to Norfolk and Suffolk a couple of times since. Further information which changed what I previously knew or assumed about SB’s in the UK.

When they started regularly ringing SB in Norfolk (since 2003) most were of the insulae race but increasingly over recent years the proportion has changed diametrically and now most of them are nivalis. It is a change they have been pondering on for some time and could be due to the Icelandic birds having had a collapse or perhaps with milder winters they have been staying closer to home, even Scotland.

It is thought that the Icelandic birds arrive in Scotland via the Northern Isles, and presumably some make their way down the west coast. The nivalis birds seem to come west across the North Sea from Scandinavia, although they may work their way home up the English and eastern Scottish coast. This would explain why nivalis is rare in the west and Wales. Previous posts reported that only around 1.2% of birds ringed in the UK were of the nivalis race but this is obviously incorrect as some are not assigned to race when ringed. Even so, the proportion of nivalis ringing in Wales may not be far off this.
H7 has been superbly photographed by Andy Thompson and annotated by Colin Carter with pointers as to age/sex/race:

Key field features include:
Tertials all evenly chestnut, not buff=adult
9th primary less than 40% white=insulae
Brown mantle

White or whitish rump feathers
Primary coverts white tipped black=1st winter male
Very frosty mantle
More than 60% white on 9th primary

Yes they’re doable!


1 comment:

  1. Good stuff Rob - an interesting one. Although 'insulae' are rightly regarded as the more 'usual' Snow Bunt along the North Wales coast, it's good to know that nivalis aren't the 'very unlikely' bird we thought it was. Certainly all Snow Bunts seen during winter or on autumn / spring passage deserve scrutiny here in North Wales.
    There seems to be three populations of three races that occur in the UK-
    Nominate nivalis from Greenland (and west), nominate nivalis from Scandinavia (and east) and ssp. insulae from Iceland.
    With this in mind, and the fact that our Lapland Bunting come from Greenalnd, surely 'western' nivalis should occur here more regularly than we think.
    Then there's always The Siberian race ssp. vlasowae which has been mooted to be able to reach the UK and has certainly arrived in Norway several times. A nice snowball male of this race should stand out a mile!

    With the other two spp. the 9th primary seems to be the key - very difficult to observe in the field though. However with video, pictures or prolonged viewing it can be seen.
    Any Snow Bunt that appears frosty mantled and with white rump feathers should vertainly be scrutinized.
    It would be good to nail a nivalis this spring here in North Wales. If only to prove that they do occur.
    Any info on these on Bardsey Steve?

    A few interesting links to Martin Garners site on the subject - check out those Siberian males!