Friday 15 March 2013

2nd-winter Thayer's Gull photoshoot

If somebody was to try and describe what a typical 2nd-winter Thayer's Gull looked like, I'd say good luck to them. Mind you, guess the same could be said about describing the same age of Herring Gull. As always, Chris Gibbins has done as good a job as anyone will and recently wrote this about the birds he saw, also in California, in December 2012. Many of his birds taken at the same sites as in the photos below - all taken in the period 16-23 February 2013! You'll notice that the Californian sun has got to a lot of birds between December and February, but structurally they remain the same - without doubt an 'in between' gull, where one moment you get an Iceland (Kumlien's) Gull-like feel and then the next it turns into an altogether more Herring Gull-like bird.

Photos 1 to 3. 2nd-winter Thayer's Gull, Milpitas, California Feb 2013 an average bird structurally, though quite retarded moult wise. No mirror to P10 with the outer primaries obviously dark due to the dark pigmentation from the outer webs bleeding onto the inner webs, and the often quoted 'venetian blind' effect created by the paler inner primaries (though in this bird the secondaries are bleached)
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

Photos 5 and 6. 2nd-winter Thayer's Gull, Jenner, California Feb 2013. Quite a pale eyed bird which interestingly shows a white mirror on P10 but the primaries are otherwise characterised by the typical thayeri pattern - dark extending onto the inner as well as outer webs of the four outermost primaries as well as bleeding up to the primary coverts. Would this bird be pushed as a thayeri in a vagrancy context over here? I do wonder

Photos 7 and 8. 2nd-winter Thayer's Gull, Salmon Creek, California Feb 2013. Quite an advanced, Herring-like bird with a mirror to P10. However, the primary pattern is fine for thayeri and the very dark brown tail band is within range, though the uppertail coverts are perhaps cleaner than average. Not sure how identifiable this bird would be in Europe though...
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 10. 2nd-winter Thayer's Gull, Petaluma, California Feb 2013. A fairly chunky looking bird, yet fairly small in the field with a slim, Iceland-like bill. Note the pale edged chocolate brown primaries and solid brown tail with brownish uppertail coverts
Photo 11. 2nd-winter Thayer's Gull, Milpitas, California Feb 2013. A fairly uniform bird, especially tail and secondary wise though the outer primaries show what you'd expect for a thayeri and there's a venetian blind effect there too. At times, I still get a slight Glaucous-winged Gull feel on this bird but this stout appearance isn't necessarily a negative for thayeri
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


  1. Hi Rich, Having seen your shots I was wondering about the extent of pale fringing on the primaries.The Garner/Gibbins article says, i think,the pale fringe should be more or less confined to the tip of the primary but some of your birds show a more extensive fringe especially on some inner primaries. Just wondering if its a more variable feature than previously suggested. Paul Moore, Cork

  2. Hi Paul thanks for the comment. I think that 2nd-winter Thayer's Gulls is yet (and perhaps never will be?) a precise science and I think that Garner/Gibbins focus on birds in December whereas a couple of months on the birds seem to show overall a lot more wear and I guess this is reflected in the primary fringing being more extensive on my visit. As an example, look at the recent Thayer's Gull in Spain (now an adult of course) when it was around in March 2010 (scroll down)