Friday, 23 February 2018

Choshi (6): Common Gulls

The last remaining gull species of interest to me present at Choshi in reasonable numbers was Common Gull Larus canus. Despite a lot of individual variation, I assume all of those I saw there to have been 'Kamchatka' Gulls L.c. kamtschatschensis. As a first-winter, this form retains more juvenile plumage until much later in the winter than other forms of Common Gull, and it wasn't that difficult to find one or two that had replaced practically nothing in their saddles.

Most had replaced at least some feathers, though, but I didn't come across any that had replaced all (as I remember being the case with L.c. canus in the UK). The most obvious variation at this age was on the underwing, with some having very dark underwings with largely solidly brown axillaries, and others having a much whiter underwings with brown-fringed axillaries. I have it in mind for some reason that white-looking underwings are a characteristic of L.c. heinei, but that these need also be accompanied by an entirely white body (without dark blotches or streaks).

Remarkably, I returned from Choshi with only one second-winter Common Gull on my camera. This, too, was a rather dirty-looking thing with its solid brown collar/shawl.

The adults were overall less remarkable than the immatures, though there was plenty of variation in wingtip pattern amongst them in just the handful I shot. The first bird below shows limited black in its wingtip, with black reaching the primary coverts only on P10 and a largely grey P8. The second bird (third photo) shows more black at the wingtip, with black on P10-8 reaching the primary coverts and a largely black P8. The third bird (fourth photo) had plenty of black at the wingtip, but also three mirrors. The last (and largest) bird has quite a long (but diffuse) tongue down P8!

So a medium-sized gull of interest to complement all the large ones. All in all, despite the best part of four days there, I still feel I only scratched the surface at Choshi and a return visit in an upcoming winter would be highly desirable! Above photos taken at Choshi Harbour, Chiba Prefecture 6-9/2/18.

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