Thayer's Gull (thayeri)
(last update: January 22, 2013)
Thayer's Gull adult, February 03 2013, Boulder County, Colorado. Picture: Amar Ayyash.
By February still much of a 'hooded' effect. Purple orbital ring, much peppering in iris, pale greenish-yellow base of bill and small red gonys spot. Classic pattern on P9 and P10, but no black on P5, a pattern found in 25% of 123 adult Thayer’s Gulls scored on P5 in central California by Howell and Elliott. Black on outer web of P5 (right wing only) and broken sub-terminal band on P10. P10 with limited black on inner web. Thayeri pattern on P10 and P9, on P9 combined with broad sub-terminal band. Medial band on P9 hardly continues on inner web. Amber iris with intense speckling.
Heavy bill suggests male. Strong bird, "Mr Big Bill". Probably younger adult, tail with some black (but sometimes adults continue to show black in tail on older age). Greater primary coverts plain grey as in full adult.
