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A Thayer's Gull in Iceland

A fourth-winter type Thayer's Gull Larus thayeri was discovered at Sandgerši (SW) on 10 March 2004, by Killian Mullarney, Pat Lonergan, Richard Millington and Yann Kolbeinsson. The bird showed quite well at times, for several hours while the tide was moving out. It stayed with hundreds of Iceland Gulls Larus glaucoides, several Kumlien's Gulls L. g. 'kumlieni', one American Herring Gull L. argentatus smithsonianus and dozens of Herring L. a. argenteus, Glaucous L. hyperboreus and Great Black-backed Gulls L. marinus. Also around were hundreds of Black-headed Gulls L. ridibundus and a second-winter Ring-billed Gull L. delawarensis. The Thayer's Gull hasn't been seen again at the time of writing (12th March).

This bird was originally thought to be adult, but a video taken by Killian showing small dark markings on the alula and primary coverts indicates that the bird probably is a fourth-winter type (5th calendar year type). Video-grabs below show clearly the primary pattern, with black on p5-p10. The complete lack of mirror on p9 (second outer-most primary) is probably linked to the bird's young age. Most if not all features shown by this bird are in favour of Thayer's Gull, but of course the possibility of some kind of hybrid (e.g. American Herring Gull x Glaucous-winged Gull) has not been ruled out completely so far... Note however some distinct features, such as the greenish colour in bill, much darker mantle (blue-grey colouration) than on the surrounding Iceland Gulls, an apparently dark eye, much brown/greyish on head and neck, pink legs, very pale and nearly uniformly looking underwings and finally the big and robust size.

This represents the 1st record for Iceland (if accepted), which comes shortly after a very interesting gull that had been recorded in January (see photos here), and is now generally thought to be an extreme Kumlien's Gull or Thayer's/Kumlien's Gull hybrid (although the possibility of it being a pure Thayer's has not been ruled out, and probably never will be....).

- YK 12/03/2004

- click on the photos to enlarge -

Thayer's Gull Larus thayeri
Sandgerši (SW)
10 March 2004

Fourth-winter type, with adult Iceland Gull.

© Killian Mullarney

Thayer's Gull Larus thayeri
Sandgerši (SW)
10 March 2004

Fourth-winter type, with 3 Iceland Gulls (and Glaucous Gull in
middle far right).

© Yann Kolbeinsson

Thayer's Gull Larus thayeri
Sandgerši (SW)
10 March 2004

Fourth-winter type, with 6 Iceland Gulls and three Great
Black-backed Gulls.

© Yann Kolbeinsson

Thayer's Gull Larus thayeri
Sandgerši (SW)
10 March 2004

© Killian Mullarney

Thayer's Gull Larus thayeri
Sandgerši (SW)
10 March 2004

Note the primary pattern (incl. absence of mirror on p9),
and dark markings on alula & primary coverts.

© Killian Mullarney

Thayer's Gull Larus thayeri
Sandgerši (SW)
10 March 2004

© Killian Mullarney

Thayer's Gull Larus thayeri
Sandgerši (SW)
10 March 2004

Note the very pale underwing and restricted amount of
black visible on it.

© Killian Mullarney