Thayer's Gull (thayeri)
(last update: January 22, 2013)
Thayer's Gull 1st cycle, pelagic California, US. Picture: Clay Kempf.
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Thayer's Gull from a Shearwater Journeys pelagic trip. Note pale crescents at the end of the dark primaries; a small bill and a nicely rounded head; a "scaled" look to the mantle with three-toned scapulars, scaled wing coverts and vent; solid dark centers to the tertials; and even a hint of the pale underside of the primaries on the bird's left wing. All are excellent field marks for a Thayer's Gull.
In the open-wing shots, note the dark outer webs and pale inner webs of the primaries can be seen well. Tail pattern and dark secondaries (creating dark bar on the trailing edge of the inner wing) are also apparent.
Last phote: Dark outer primary webs and pale inner primary webs result in the appearance seen on this photo. On the bird's right upperwing, primaries appear dark, as the outer webs are visible and inner webs mostly obscured by the adjacent feather. The left wing shows the opposite effect, where the pale inner primary webs are quite visible from the underside while the dark outer webs are obscured. The resulting impression is one of very pale underwings. This combination of field marks is indicative of first-cycle Thayer's Gull, and holds true through subsequent molts and into adulthood.