Happy to be corrected, as allways with large Gulls.
Is this the same bird, it seems to differ at least in pattern of greater coverts and tertials?
I just comment on the second picure (=second bird?) Because, in this, I see nothing wrong for the default species, a 1 winter Yellow-legged Gull (2 cy, if taken in january 2021).
Its hard to be certain with picture quality seems to obscure/fade out the relevant details, but:
quite dark greater coverts fading into a more variagated pattern
dark tertials with just the right pale unnnotched margins
-all dark bill in a good shape
-pale head with pattering around eye, reaching to the neck
-the right dark grey mantle and the right dark centers to mantle feathers
Everything SEEMS to be there. Yes, I know this cant be judged with 100% confidence here, but it fits the default species so well, that it seems an idable YLG to me, even with such a unsharp picture (no offense!)
If first bird is a different individual and the appearant appearance is real, this is a harder picture, and I would learn from the experts here:
- long, slender bill with drawn out head-profile
-ginger washed out neck-band
-extensive pale, whitish creater coverts with just a few dark markings
pale grey mantle with narrow shaft streaks (=cachinnans-pattern). But this seems extremly hard to tell, and I get the impression, thsat this pattern is a result of picture quality and artefacts.
paler tertials compared to the second picture with wider pale edges.
Conclusion? First bird is an "experts, please help-Gull", at least to me. Second, if its different, is an IDable 1-winter YLG to me.
all birds depicted are 1st winter Larus michahellis. most things which alexander wrote are correct and worth considering, but there's a lot of variation so, some herring gulls virtually can look identic to some yellow-legged gulls in first winter. but not these. actually you rather have to separate them from the abundant Lesser Black-backed Gulls wintering in the area, which often is not that straightfort. as for the blurry shots in the fisrt post i can't guarantee they're not Larus fuscus.