[Switzerland] Yellow-legged Gull (1 Viewer)

Hello all,
A few Caspian Gull have been recorded at that place in the past few week, but without picture. I don't think I found them but I just wanted to check with you that these are all YLGU.

On the first picture, I have doubt about the second (head not visible) and fourth (turning toward the left). Head shpe, miror and bill length look not good but long legged, small eyes and good position...

On the third picture, I just wanted to make sure that it's not a 1w Herring, look pretty dark headed, small and thick bill, but I don't know how to read the coverts pattern...

Thanks for your help!

Cheers,

these are all YLG. including the 1w.

Look like the third picture is not online... here it is...

what catches the eye first are the multiple replaced, 2nd generation wing coverts. this already makes it an almost safe michahellis (which it is). herring gulls usually don't replace any wing coverts during postjuvenile moult.
add the high, stubby and all black bill, the very worn juvenile coverts and the blackish (instead of dark brown) primaries lacking an obvious pale crescent at tip (well, most of it could be worn off even in most HGs, but there might have been some rests of it towards the inner primaries)

Hey Lou,
Thanks for your detail answer. I'm trying to learn! Can you look at my annotated image to see if I correctly understood your description?

Thank you so much, It's really great to be able to understand more about these very challenging ID.

yes, mostly. the area of replaced coverts sticks out a bit more to the rear, including 2 nicely exposed inner greater coverts, pale crescent on inner primary is normal, also in micha but usually more pronounced in argentatus - variable! worn coverts not by the pale margins, coverts in fact do have whitish fringes but these wear off fast, usually faster in YLG. of course by late winter most large gulls have worn coverts but the extent of bleaching and wear is obvious in this bird. usually there is some white left in HG juv coverts while these make a plain brown panel in the wing. note that quite some michahellis have dense head streaking after postjuvenile moult in spetember-october, like in this bird, and strongly marked underparts - often causing confusion with herring gulls. of course the easiest way in dark birds is if they take off and you see their tail and inner wing