lamby lake

I have just witnessed Gull behaviour i haven’t seen before.A flock of 20 or so Black Headed Gulls appeared to be flying around and hovering over lake-side trees laden with berries.I was 200yds. away with just bins.They seemed to be actually taking berries,but couldn’t be certain.On reaching my car i got my scope out and eating berries was exactly what they were doing.Has anyone else seen or heard of this kind of behaviour?