Plate 1: Examples of wingtip scoring criteria for dark markings on the outer primaries.
From: Identification and Variation of Winter Adult Kumlien’s Gulls, by Steve N.G. Howell & Bruce Mactavish, IN: Alula 1/2003.
0: no visible darker grey markings relative to the grey basal and white distal portions of the feather;
1: darker grey markings restricted to the outer web or shaft area but with no dark subterminal marks;
2: grey markings include a partial subterminal "band" (<50% of the feather width);
3: grey markings include an incomplete subterminal band (50-99% of the feather width);
4: grey markings include a complete narrow subterminal band (< width of white primary tip);
5: grey markings include a complete broad subterminal band (≥ width of white primary tip).
A band split only by a fine white shaft streak did not qualify as an incomplete band (e. g. P7-P8 in Photo below).
"Iceland Gull" adult, March 01 2010, Njardvik, SW Iceland. Picture: Hans Larsson.