Table 1: Wingtip darkness scores for 185 adult Kumlien's Gulls in Newfoundland.
From: Identification and Variation of Winter Adult Kumlien’s Gulls, by Steve N.G. Howell & Bruce Mactavish, IN: Alula 1/2003.
For the darkness of the grey pattern on the wingtip, we used six gradations from white to blackish grey, as follows:
0 - white (Kodak 0);
1 - pale grey, similar in shade to upperparts and primary bases (Estimated Kodak 3-4);
1.5 - medium-pale grey (Estimated Kodak 5-6);
2 - medium grey (Estimated Kodak 7-10);
2.5 - medium-dark grey (Estimated Kodak 11-13);
3 - blackish grey (Estimated Kodak 14-17).
Values relative to the Kodak Grey Scale (catalogue number 152-7662; whereby 0 = white, 19 = black) were estimated by Howell, but should only be viewed as approximate, given the inherent difficulties related to ambient lighting, the angle at which the bird is standing, and observer perceptions under variable field conditions. For example, wingtips of score 2 can easily look darker (2.5 or even 3) in low light (such as late in the day) or with backlit reflection for birds standing on ice. Photos of birds against ice and snow often tend to be underexposed and, thus, misrepresent wingtip shades.
In a sample of 190 birds, the inner web and outer web portions of the subterminal bands were not appreciably different in shade on 184 birds (97%), while on six (3%) the outer web appeared darker than the inner web by one category (cf. wingtip scores). Grey markings on the outer four to five primaries were overall similar in tone, perhaps with a tendency for markings on P7-P8 to average darker or at least more "solid", than those on P6 and P9.