Very odd this. Just a few days before Christmas all the gulls were sitting on the roof of a neighbouring building at first light.
An assortment there, Black-headed, Common and Herring. There were loads more than shown in this picture (probably about 30) and they flew to the garden, back to the roof, round and round for about an hour.
Then they all disappeared.
I've not seen this before, nor since. I was trying to get flight shots... but didn't do too well LOL.
TTTW