GullDK: Possible Kumlien's Gull (Larus [glaucoides] kumlieni), 3cy, 23.01-03.03.2012, Thyborøn Harbour

Wednesday 9 July 2014

Possible Kumlien's Gull (Larus [glaucoides] kumlieni), 3cy, 23.01-03.03.2012, Thyborøn Harbour

Case: 2013-169
Date: 2012-01-23 -(03-03)
Site: Thyborøn Harbour, Denmark
Observer: *Henrik Haaning Nielsen, Allan Kjær Villesen m.fl.

From these photos alone it seems not safe to exclude a well-marked Iceland Gull (Larus glaucoides) though this is not to say it is not Kumlien's Gulls. It has without doubt some dark shading on the outer webs of the outer primaries with the colour being darker on the outer than on the inner web, but the flight shots do not seem to show a clear Kumlien's/Thayer's pattern on the outer. Even though the dark shading on P7-P9 reaches the primary tips, the dark pattern does not seem to penetrate onto the inner web, i.e. the bird seems to lack the dark hook-pattern on the inner web. It is also difficult to determine whether there is a faint 'ghost mirror' on P10. This could be caused by the state of the plumage which seems to be rather bleached and especially so on the last photos which were taken in March. As a result it does not seem safe to exclude a well-marked glaucoides.

Note that it is not abnormal for 2nd- and, especially, 3rd-cycle glaucoides to show a brown wash on the outer primaries. The plumage of such well-marked immature gulls often looks quite retarded, with still lots of brown in the wing. Note that the brown wash on outer primaries of such birds simply matches the brown wash on outer secondaries, as is often the case in other 3rd-cycle gulls (e.g. Herring Gull). It is therefore considered just to be a trait of immature plumage.