lesser black-backed or yellow-legged gull ? Cardiff (1 Viewer)

[marnixR]

i assume that the attached is more likely to be a lesser black-backed gull rather than a yellow-legged one, but something made me doubt myself, thinking that the colour of its back was more dark grey rather than black

which brings me to the question : how would i distinguish between the two ?

pictures taken earlier today in Penarth Marina

 

[Andrew Whitehouse]

Lesser Black-back. Too dark for Yellow-legged and also the streaking on the head is a bit heavy.

 

[marnixR]

so it's mostly the colour of the back then
it's just that to the naked eye the colour appeared to be less black than it shows on the images