According to the Royal Society for the Protection of Birds, a change in society has attracted gulls to the cities.
Tony Whitehead, from the RSPB, said pre-World War Two gulls did not nest in towns and cities but a shift in people's behaviour and attitude towards food has made urban spots attractive nesting grounds.
"It is because of all the rubbish," he said. "Prior to 1940 we produced very little organic waste. We were very good and ate all of our food and any bit of rubbish was burnt on people's fires.
"It is a sign of the times that we can afford to get rid of food.
"Gulls are classic scavengers and it doesn't matter if it is great big rubbish tips or bags of rubbish on the streets."
Mr Whitehead said a change in building design has also created an ideal environment for the birds.
"Architects after the war designed buildings to look like beaches with flat roofs covered in shingle," he said.
"We provided them with food and a nest and then we are surprised to see gulls in towns and cities."