Here are some of the Common Gulls I came across in Istanbul. according to the Peter Adriaens & Chris Gibbins paper from Dutch birding a couple of years ago Istanbul was a research location for heinei Common gulls, most of what I was seeing were likely from decent ‘Russian’ stock, they did have that look and showed:
- A Clean white, mostly un-streaked head (I feel this must be a highly important feature as I am yet to see canus show this!) with Casp-like neck Shawl
- Pink Bill base
- Clean white rump and upper tail, a neatish thin Black band with little or no white in outer web of t6
- Mostly White underwing, contrasting with dark secondaries
- A long winged appearance
- 2nd generation Scapulars are darker than canus, many with brown chevrons and markings contrasting with the darker choclately remaining wing coverts, (unless bleached as some were)
The next few birds shows some head streaking but give a similar feel to me in terms of the tones in the wing and mantle, could well be from an intergrade zone or just variation … dunno
The Below photo was taken in Cyprus December 2016, a similar thing going on, long winged, bug eyed thing.
Ive seen a few Candidates in the UK, with one in particular showing almost every feature but the usual let down over here is the lack of an un-streaked almost pure white head which I suppose gives that impression of a small round head with a large eye and the expression seen on the clean headed birds above. According to the BBRC heinei common gulls are something along the lines of ‘probably only scarce’ due to a number of birds ringed in a catch of common gulls being assigned to heinei on biometrics (mainly wing length i think) i’ve never seen one that looks exactly like theyre supposed to in the paper although id hope it was a possibility. Keep looking.