Mediterranean Gull Ichthyaetus (prev. Larus) melanocephalus
The Mediterranean Gull has pale silver-grey wings on a white body. Breeding plumage includes a black head with white eye-liner and red bill.
Winter plumage - mainly white head
Winter bill: horn coloured or orange
On the turn from winter white face to summer black face
Winter plumage is a mainly white head with grey shadow and a horn-coloured, dark-tipped bill.
Previously prevalent mainly in the eastern Mediterranean and the Black Sea, it has become more common over the rest of Europe,
including the UK, returning south in winter.
Comparison with (chocolate-headed) Black-headed Gull
The ringed Mediterranean Gull above was among a flock of Black-headed Gulls in winter/early-spring in London, UK.
Links:
Black-headed Gull