An interesting gull 11 December 2011

Ämmässuo, Espoo Finland. This bird, found by Markku Kangasniemi and Hannu Koskinen, was quite difficult to identify. It is quite similar to a Caspian Gull Larus cachinnans, but could be a hybrid with Herring Gull Larus argentatus (which is the common species at the location in question). Many of the features are good for cachinnans, but we feel that this individual is somewhat wrong-looking to be a pure cachinnans.

This bird had a call quite similar to cachinnans. In this recording there are first some harsh, short calls, then a long call, which has quite a protracted last part and last, the normal, cachinnans - like long call, which it used quite a lot.

Not so long billed, but perhaps ok for a Caspian. Scapular pattern very much like a Herring gull. Quite pale and partially barred greater coverts, not very good for a cachinnans and also a tertial pattern not very typical of a Caspian Gulll.

On the other side, the tertial pattern was somewhat different. The streaking on the neck is good for cachinnans. No moulted coverts.

Dark upperwing is good for cachinnans and too dark for a normal argentatus. Underwing pattern - not typical for cachinnans, but possibly not impossible.

Another shot of the dark upperwing

And the underwing.

The tail pattern was good for cachinnans, but the upper tail coverts are perhaps not quite so good. Still, this photo lies, see photo in flight which shows much more white on the upper tail coverts.

One more underwing photo.

The bird uttered the long call quite often.