Herring Gull (argentatus & argenteus)
(last update: February 11, 2013)
Thayer's Gull thayeri 2nd cycle (3CY), December 28 2012, Half Moon Bay, CA. Picture: Chris Gibbins.
This is a typical second cycle bird, although they are highly variable. Tertials extensively solid dark brown lacking vermiculation at fringes. Note the rather solid brown, slightly marbled greater coverts, typical on most gull species in second cycle. The amount of adult gray in the mantle is highly variable at this stage. Notice the contrast between the outer and inner webs
and the dark reaching the primary coverts on the outer 6 (perhaps even 7) primaries, the lack of any
mirrors and the dark secondaries. In large gulls the outer web of primary 10 is always narrower than it
is on the other feathers. Because of this, on taxa such as Thayer's and Kumlien's which have a contrast
between the outer and inner webs, the dark on primary 10 appears more restricted than on the other
feathers. Bear this in mind when assessing dark versus pale areas.
