There are three locations: the west facing northwest corner, the north facing northwest corner northeast of the first, and a north facing area in
Cantabria well to the east of the other two.
I may have missed them, but I didn't note any Herring Gulls. There were a few Great Black-backeds and Black-headed Gulls in Viveiro. There was a
juvenile Lesser at Santona.
All of the adults have a pale ashy gray mantle. All but one (at Viveiro) have black shafts on the primaries. In most of the adults P4 is unmarked, but some
have a small black spot on P4. There is no bluish cast to the mantle. The mantle is much paler than any Lesser Black-backed. I would say it is close to
the shade of North American Herring Gulls, though of course there were none around for direct comparison. These birds do not look at all like the classic L. m.
michahellis from the Mediterranean. Maybe I am wrong, but I don't think many gull observers in North America realize how different these birds are from
michahellis (which are larger and bulkier), and also from atlantis (darker mantles). These birds have rounded heads. Around March 1996 I had a YLGU of
this type at Hatteras NC.
For comparison, here are some YLGUs from elsewhere:
Many YLGU photos from Norman van Swelm