Anybody that can help with this bird?
We thought it was cachinnans first day when we only saw it on water, the bird are very agressive and the voice is good for cach as well. It have some pale areas on the outer webs of the inner primaries that maybe are not to good for cachinnans, but possible, I presume. It is very different from our herring gulls nowadays, very low in water and whiteheaded.
Yesterday it showed well on the ice as well, it have quite short tibia and no white areas under the wings. And the bird are quite "stocky", not elongated as we normally see in cachs.
Probably cach x arg, or is this possibly an eastern type of arg?
All the best,
Morten
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On the other hand, the pure knowledge of existing hybridizasion in nearby colonies makes things more complicated, to say the least! With some regularity strange 'cachinnans' turns up and confuse everyone, some of these shows quite clear how they are 'constructed', some are more difficult, some are impossible, and a few of those imposssible are in imo strange looking argentatus. Regarding the subject gull, the imediate impression is not a pure cachinnans, but then of course you have to reexamine all features in good faith for a positive identity - which is easier said than done. The inner primary pattern - with paler outer webs - creating dark obvious dark subterminal tips is not associated with typical cachinnans, an argentatus/argenteus character. Instead of focusing on to many plumage features, which might only confuse even more - a few major features to be on the safe side, such as inner primaries, scapular pattern (which vary according to wear and a certain variation), tertial pattern, bill structure/shape, underwing pattern and of course moult and overall structure. One could think that the bill is on the short end for a pure cachinnans but that might not be so at all, since sexual and individual variation has to be considered, there are some short-billed ones out there. Further more, the axillaries pattern might suggest other than cachinnans but even those are apparently subject to a certain degree of variation. Other features - such as greater covert pattern is variable - some show unexpected pattern there (which also can be seen in varies pic on the net), but otherwise looks perfect for cachinnans. Leg lengt is of course also variable according to stance and so on, but they do look short on the subject gull, that is to say the tarsus, which is the visible part here. The tail pattern is not entierly of for a cachinnans, but the pattern of the base of the t-feathers might suggest otherwise - but see here for rather similar patterns (