The Danish gull now versus a Thayer's from California

Peter Adriaens wrote me and said: “one of the Thayer's Gulls that I photographed in California is called into question - once more.

It is this bird

Thayer’s Gull: from top left to right bottom: 1-4: (same individual) 28.1.2011, Bodega Bay, California, Peter Adriaens; 5-6: (same individual) 4.2.2012, Hvide Sande Harbour, Denmark, Kent Olsen. Note that the upper left photo was taken 2 seconds before the one in upper middle, and the upper right was taken when the bird had landed just 6 seconds after the one in the middle.

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I hope that at least the photographer (me) is allowed to defend the identification of this bird? It amazes me that people approach identification of Thayer's Gull with extreme caution, yet need just one photograph to dismiss it as a hybrid - which is often even more difficult to identify than the real thing!

I have two more photos of this bird and Kent has put them together here. Note that the upper left photo was taken 2 seconds before the one in upper middle, and the upper right was taken when the bird had landed just 6 seconds after the one in the middle.

Also, I spent almost a full day at Bodega Bay then, together with Steve Howell. We discussed and photographed many of these Thayer's-like birds, and this one was not a problem.

My reasons for identifying this bird as Thayer's Gull as opposed to Glaucous-winged x American Herring Gull were (and still are):

- relatively small size
- thin, parallel-sided bill
- slimmer, more elongated body than other large gulls, with fairly long primary projection
- strong dark peppering on inner primaries (usually absent in GWGU and AHGU, but often seen in 'good' Thayer's Gulls); I have attached a crop of the outer wing so this can be more easily judged (lower left). Note also the obvious white tips to the primary coverts, though I am not sure if these are useful as a character.
- distinct but irregular barring on greater coverts (usually plainer pattern in GWGU and AHGU, especially in the former species)
- full juvenile plumage (in late January)
- frosty, almost whitish appearance of scapulars

To my eyes, nothing seems wrong for Thayer's Gull here, but I am eager to learn so I hope that people who feel that this is more likely a hybrid could somewhat explain their reasons? I suspect it was the apparent bill shape in this photo that seemed wrong, but as anyone who takes photographs of gulls will know, a bill often looks heavier than in reality when turned away from the camera. In addition, note that the bird holds its bill slightly open in flight, adding to the heavy impression in the photo.

Anyway, I hope this explains things a bit.

Best wishes

Peter”