Thayer's Gull (thayeri)

(last update: January 22, 2013)

Thayer's Gull - Plate 1.

From: Identification and Variation of Winter Adult Thayer’s Gulls with Comments on Taxonomy, by Steve N.G. Howell & Martin T. Elliott, IN: Alula 4/2001.

Plate 1. Comparison of winter adult Thayer’s Gulls, American Herring Gull, and hybrids.

Top row (left to right): "older/pale-winged" adult male Thayer’s, two large (male) adult Thayer’s, small adult (female) Herring, adult (male) Glaucous-winged x Herring hybrid, and adult Glaucous-winged x Western hybrid.
Bottom row (left to right): small "young" adult (female) Thayer’s, atypical female (intergrade with kumlieni/glaucoides?; same bird as Plate 3, n), pale-headed adult female Thayer’s, and small (female) adult Glaucous-winged x Herring hybrid.

The intent of this plate is to illustrate extremes of sexual size dimorphism (left-hand two figures), head streaking, and bill colours of winter adult Thayer’s; relative differences in upperpart tones between Thayer’s and congeners; and apparent differences related to the angle of lighting (note that birds are shown in shadow on a clear evening, which exaggerates blue tones). No attempt should be made to infer Kodak values here, as colour reproduction and printing, like field conditions, make accurate assessments extremely difficult. Based on birds video-taped in California, December I999.

© Martin T. Elliott.