29 January 2014

1st Cycle Thayer's Gulls from California

Below is a collection of 1st cycle Thayer's Gulls photographed in central California in mid-January (2014). A week-long trip here allowed for good study of this species with some 600 individuals sighted, ~ 170 of which were first cycles. Photos sets of 2nd cycles, 3rd cycles and adult types are also available.

Routine comparisons were made with the main confusion taxon, Glaucous-winged x Herring (so-called Cook Inlet Gull), and I've made an effort to exclude birds showing bulky proportions and bills from this set. A forthcoming post on Cook Inlet types will soon follow. I welcome any comments you might have.


  1. bird 2 looks very borderline on the Hampton scale for Thayers, except for the primaries which look to be a 3. the primaries seem to be the easiest/most informative of all the Hampton criteria, just in terms of separating Thayers from Kumleins/Iceland if 2 or below?

    1. Hi, Andy. Yeah that 2nd bird looks a bit bleached and faded. The pale base to the bill also makes it look more "borderline". As you say, the primaries are good places to start when assessing Kumlien's/Thayer's. An open wing and tail are, needless to say, very helpful. You'd be looking for a darker secondary bar and more contrasting and dark tailband.

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