Journey man is correct – gulls (not seagulls).
65 years, or so, ago I remember Dad commenting when we saw a couple of gulls flying over at considerable altitude. Likely one way was spring and opposite direction autumn? Certainly not a common sight.
In those days lapwings were really common and followed the plough. 30-40(?) years later lapwings were far less common and gulls followed the plough. Nowadays nothing much follows the plough because the soil has been made devoid of bird-edible fauna by continued use of pesticides and inorganic fertilisers!
50 years ago the gulls started to occupy the local flooded clay pits which were starting to be filled with household (and other) refuse. Nowadays they live wherever there is an abundance of food to scavenge.
Schools in the local city are inundated with gulls from the local tips at every playtime, when there is lots of food discarded by the school children with dirty habits. About 20 minutes after classes restart, the playgrounds are stripped of ‘pupil droppings’, and the gulls have departed, leaving behind their own droppings.
Such is progress. Come back the 1950s-1960s, I say.