Explanation for the measurements of P5-P10 patterns in adult glaucoides and kumlieni.

Illustrations after Plate 2 from: Identification and Variation of Winter Adult Kumlien’s Gulls, by Steve N.G. Howell & Bruce Mactavish, IN: Alula 1/2003.

“Adult” primary patterns of presumed Kumlien’s Gulls Larus [glaucoides] kumlieni (a-o), possible hybrid Kumlien’s x Thayer’s gulls (p-q) and an “average” Thayer’s Gull for comparison (r). All wingtips taken from birds seen in Newfoundland, Canada, during February 2002, except for Thayer’s Gull (from California, December 1999). Figures are arranged to show progressive development of wingtip patterns from all white to most extensively and darkly marked. Percentages in parentheses are relative frequency of Stages 0-6 in a sample of N = 345 birds. Original drawings: © Martin T. Elliott.

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Figures d-f: Stage 2 (11%), darker grey marks on the outer three to four primaries with subterminal marks on one to three primaries.

Figures g-i: Stage 3 (12%), darker grey or more extensive grey marks on the outer four primaries with complete subterminal bands on one to three primaries.