Herring, Bonaparte's and Ring-billed Gulls off Prairie Dog Point, Lake Hefner
WD: Bonaparte's Gull in front, Thayer's Gull behind, Herring Gull to the left, two Ring-billed Gulls and a Herring Gull to the right. The Bonaparte's doesn't have the black rear crown or white primaries of a Little Gull. The Thayer's is smaller than Herring Gull with a slightly darker back, a darker eye, larger white tips on the primaries, shorter primary projection and less extended body, rosier pink legs, a smaller and rounder head, smaller bill with less gonydeal angle, brighter red spot with no dark smudge and relatively large and contrasting tertial and scapular crescents (white areas). When we see a gull that shows some of the characters just listed, we look to see if the underside of the far side primaries is all light or almost all light. In this case there is a large white spot with no subterminal black band indicating the mirror and white tip are merged into one large white tip, another point for Thayer's. Not apparent on this Thayer's are shorter legs than a Herring. There is no reference light eye in the picture with the same exposure as the Thayer's eye and Bonaparte's eye to calibrate the eye color in the shade, but the wealth of other Thayer's marks leaves no doubt. Not all Thayer's have such dark backs that they can be distinguished from Herring and Ring-billed, i.e. they are closer to Kumlien's Gull in the spectrum of Thayer's-Kumlien's-Iceland.