Strange goings-on at the Dale gull roost

A strange gull roost at Dale this evening.  It is usually (in fact, always) a small gull roost made up mainly of Black-headed Gulls, smaller numbers of Common & Mediterranean Gulls, and a few larger gulls (maybe 20 or so Lesser Black-backed Gulls).  I thought it might be a decent sized roost tonight as Dale offers decent shelter from a north-westerly, but I was not expecting a roost consisting of almost exclusively large gulls, and most of them adult Lesser Black-backed Gulls.  Perhaps the wind direction had put them off hopping across to Skokholm (where I presume most of the large gulls passing over Dale village are heading to)?  There were around 1,000 Lessers, a few Herring Gulls, and I managed to pick out 2 adult Yellow-legged Gulls (LBBG is a good carrier species for them).  The small number of Black-headed Gulls were roosting beyond the large gulls, and after I had picked out 10 Mediterranean Gulls I then scanned further left (north) and realised there was a hefty small gull roosted formed towards the Gann!  The Lessers had clearly stolen their spot at Dale.  With fading light and distance to contend with I probably under-counted, but I had a minimum of 46 Mediterranean Gulls (all adults, except 2 first-calendar year (1CY) birds).  Also at Dale 3 Great Northern Divers feeding close inshore.