Sex, age and race.
In answer to the questions I posed to myself and others this is where I’ve got. My gut reaction to begin with was that the bird was a female, probably an adult and I wondered if it was of the nominate form nivalis. I’ve looked at it more closely, I still think it’s a female (scapular pattern, all dark primary coverts, underwing appears greyish on video grabs, too much dark in primaries and secondaries). I think it’s most likely an adult (tail feather shape and shape of internal patterning on the tail, broad rusty fringes to tertials though with castellations). Though I found it hardest to race it and having checked my video the pattern of P9 (descendent numbering), looks equivocal (some pattern can be diagnostic for race) and most of the secondaries have obvious dark tips (kind of more insulae than nivalis in pattern I think). So while the bird does look quite pale above the wing pattern suggests the much commoner Icelandic form subspecies insulae. I suppose I feel equivocal with perhaps I bias towards insulae. I won’t give up trying to separate the races I but its a real and complex challenge. Will usually need full open wing information for females and males (especially adults) are definitely easier, white rump = nivalis black rump =insulae.
Thanks to all who commented and ‘had a go’.
3 photos of the Sheffield Snow Bunting below, January 2012 © Andy Deighton