Iceland Gull in St. Louis County
2013-12-01

'Rare Regular' in Minnesota

Adult-cycle Thayer's Gull (Larus thayeri) with yellow irides observed by Jan and Larry Kraemer, and Peder Svingen at Canal Park, Duluth, 1 December 2013. I also photographed this bird at the same location 28 November 2013. A very small percentage of thayeri can show yellow irides, but Karl Bardon pointed out that close scrutiny of digital images usually reveals a few flecks of brown pigment. Perhaps its eye color reflects introgression with "Kumlien's" Iceland Gull (L. glaucoides kumlieni). This individual otherwise appeared to be a "normal" Thayer's Gull, with rather uniform streaking over its head, neck, and upper breast, a broad white tertial crescent, and generous white apical spots on its folded primaries. Its dorsal wing tip pattern in flight was also typical for thayeri with a dark subterminal bar on p10 (kumleini shows a white terminal mirror on p10), black along the distal outer web of p9 (kumlieni shows a white tongue-mirror extending across the outer web to meet the white terminal mirror on p10), and dark subapical markings on p5 (typically unmarked on kumlieni). Though not diagnostic, its mantle shade was indistinguishable from nearby American Herring Gulls (some thayeri are shaded slightly darker than smithsonianus, but we have not found this criterion reliable along the North Shore of Lake Superior).

Peder H. Svingen