It is a case of educated guesswork based on experience, gut feel along with a number of plumage characters that when pieced together get you to a second-winter Thayer's Gull. However, with just a week to play with, it was a steep learning curve so hopefully this load of shots will be useful. Certainly compiling and writing about them has been useful to me so please do enjoy and do comment.
|Photo 4. 2nd-winter Thayer's Gull, Jenner, California Feb 2013 a long-winged bird showing the neatly fringed brown primaries, 'fat feathering' that sometimes this species seems to show on its throat and solidly brown based tertials|
|Photo 9. 2nd-winter Thayer's Gull, Petaluma, California Feb 2013. Perhaps a fairly typical bird, with chocolate primaries fringed pale, obviously dark tertials and note the rather squat appearance caused by quite deep pink legs|
|Photo 12. 2nd-winter Thayer's Gulls, Milpitas, California Feb 2013. Two contrasting birds in terms of moult, as well as the bird in the foreground appearing more snouty. Both are typically long-winged with dark brown primaries|
|Photo 13. 2nd-winter Thayer's Gull, Golden Gate Park, California Feb 2013. Close inspection shows a pale eye on this bird. Otherwise fairly typical with a mantle shade coming through that is a tad darker than American Herring Gull|