Distinct pale fringes to the outer primary tips are not unique to Thayer’s Gull; first winter Herring Gull can also show this feature to a varying extent, from narrow pale fringes on darker primaries to brad creamy-white fringes on bleached ‘milky coffee’ coloured primaries. The wing tip may then lack the contrast shown by most Herring Gulls at rest, and in flight such individuals can exhibit a pale underwing (including all the primaries) reminiscent of Iceland Gull as well as pallid upperwing with light brown wing tip and secondary bar.
As we see such extreme individuals among local breeding birds in Denmark one could argue that these are pale extremes of the variation within argentatus Herring Gull. However, some of these gulls with extensive white coloration also recall birds labelled as hybrid hyperboreus x argentatus (Viking Gull). Because the plumage in this gull photographed on December 30, 2013 in Hanstholm Harbour, lacks a clear influence from Glaucous Gull when it comes to pattern on each feather, it is considered to be a European Herring Gull with reduced pigmentation, but it will always be a question whether to name it aberrant/pale end argentatus or Viking Gull-type.
As we see such extreme individuals among local breeding birds in Denmark one could argue that these are pale extremes of the variation within argentatus Herring Gull. However, some of these gulls with extensive white coloration also recall birds labelled as hybrid hyperboreus x argentatus (Viking Gull). Because the plumage in this gull photographed on December 30, 2013 in Hanstholm Harbour, lacks a clear influence from Glaucous Gull when it comes to pattern on each feather, it is considered to be a European Herring Gull with reduced pigmentation, but it will always be a question whether to name it aberrant/pale end argentatus or Viking Gull-type.
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