They tear open rubbish bags looking for food, swoop down on passersby and steal their sandwiches, and even swallow rats and squirrels whole.
Many people complain about the menace of urban gulls, but with the wild populations of some species in severe decline, our parks and high streets are increasingly the only places where gulls are thriving.
So should we fear these plucky scavengers or admire them?
One of the UK’s leading urban gull experts, Peter Rock, is the man to ask. He has been attaching identification colour-rings to gull nestlings in Bristol, Bath, Cardiff, Gloucester and other towns and cities since 1980.
“It doesn’t matter what I’m wearing, they recognise me – even year to year,” says Rock, entering a flat-roofed college building where several pairs of gulls build their nests. “Roughly translated, they are saying: ‘Get off our land.’”
Armed with a net, some pliers and a string of identification tags, Rock plans to catch recently hatched nestlings and ring their legs, to help gain a better understanding of how lesser black-backed gulls and the other main urban gull – the herring gull – are changing over time.
Gulls haven’t always occupied towns and cities to the extent they do today. A decisive event was the passing of the Clean Air Act in 1956, which forbade the burning of rubbish, resulting in increased amounts of waste food being buried in landfill. “People complain about urban gulls, but they’re here at our invitation,” Rock says. “My role, as I see it, is to discover who these birds really are and provide that information to all.”
With so much food available, more adult birds survived and were able to raise more of their nestlings to fledglings. As traditional breeding sites on islands and coastal cliffs were outgrown, gulls began seeking new breeding sites. “It was obvious, really,” says Rock, as he gestures at the stretch of tall, flat-roofed buildings: “To gulls, these are all islands with very steep cliffs.”
Urban living also has other advantages, including warmer temperatures, abundant food and few predators.
Meanwhile, changes to the fishing industry, pollution and habitat destruction have contributed to severe declines in wild gull populations – herring gulls and lesser black-backed gulls are on the UK birds of conservation concern red and amber lists.
These birds have been bothering Bristolians since 1972, when a pair of herring gulls decided to set up nest there. By 1976, they had been joined by breeding pairs of lesser black-backed gulls too.
On the college building’s roof, the screech of gulls is deafening, and the floor littered with chicken bones – presumably foraged from late-night takeaways. Armed with a net to capture nestlings as well as deter attacks from adult birds, Rock marches towards the perimeter wall and plucks three well-camouflaged nestlings off the ground, slipping each one gently into its own cotton bag.
Although several adult birds swoop at him, Rock says true physical attacks by gulls are rare. (Snatching food is another matter.)
Rather, this swooping behaviour is a warning to get off their territory. If it fails, a gull may escalate to defecating or regurgitating on an intruder: Rock was once showered in recently swallowed Pot Noodles. When physical attacks do occur, they tend to come from behind, and involve gulls striking people on the head with their feet.
Rock sits down and gently pulls the bag away from one of the nestlings’ legs. He fits a dull metal ring above its foot, inscribed with a long number and details of who to contact if the bird is found dead. On to the other leg, he slips a larger, bright red ring inscribed with two letters separated by an equals sign. This ring enables him to identify any of the thousands of previously ringed gulls using a telescope or binoculars. Finally, he measures the length of the gull’s head, wings and, after wiping away a glob of brown-grey sludge, its beak. These measurements will determine the sex of each nestling.
“Looks like worms are on the menu today,” says Rock, placing the young bird down on the ground and watching it scurry back to its hiding place.
This research has already afforded various insights into the lives of urban gulls. One is that they rarely return to the wild to breed. Instead, male gulls generally return to their natal colony (where they were born), while females seek out other urban colonies. Female gulls also breed with males from other urban colonies. They’re surprisingly long-lived: the longevity record for both species is just short of 35 years and Rock’s oldest bird is 28. “Perhaps she or, certainly, others will outlive me,” he says.
Although urban gulls will happily feed on discarded chips and takeaways, Rock’s research has revealed that much of their food is foraged from elsewhere – with roughly a third of their time spent in rural green areas, where they’ve been observed paddling for worms – luring them out of the ground by tapping their feet.
They have other cunning tactics too. A few years ago, Rock and his colleagues attached GPS tags to 12 Bristol gulls and tracked their movements during migration as well as throughout suburbia, across a school playground, rubbish dump and park. Doing so revealed that the gulls timed their arrival at these sites to coincide with the availability of food – appearing shortly before school breaks and lunchtimes, the delivery of new waste to the dump, and when worms and insects were most plentiful at the park or farmland.
Separate research on Brighton’s herring gulls has suggested that they even decide which sorts of snacks to steal by observing human preferences: given a choice between two crisp packets, the gulls overwhelmingly went for the same colour bag that a human researcher was munching from.
They’ll even resort to piggy-backing pigs to get a free meal. In Suffolk, farmers became so incensed with gulls grabbing the pigs’ food that they fixed thick strips of plastic to their feeding hoppers. “Theoretically, the gulls couldn’t get at them, but what they were doing was pitching on to the pigs’ backs, grabbing the pig nuts as they were having their nosh, and then flying back out again,” says Rock. “They even soaked them in a small puddle before feeding them to their offspring.”
Snatching food directly from humans is a relatively recent phenomenon. “It used to be confined to certain parts of Cornwall and Jersey, but it seems to be spreading,” Rock says. “The capital of food-snatching is St Ives in Cornwall, and they are absolute experts at it.”
He believes their tactics have been getting more sophisticated over time. “Some of them are working in pairs. One will fly at you, looking like it’s going to snatch your pasty or ice-cream, and as you move your arm away the other one will fly at you and snatch it from behind,” Rock says.
“Gulls are constantly demonstrating how clever they are – possibly not quite as clever as the crow family, but they’re surprisingly smart and hard to outwit.”
They’re also difficult to deter. Rock walks to the high parapet at the edge of the roof, and points out the various spikes, nets and even a broken plastic eagle-owl that have been fixed to rooftops to try to prevent gulls from nesting there. He says the vast majority of such methods are ineffective – the gulls simply push them aside or perch on them – while poorly maintained nets entangle gulls, resulting in a slow and painful death. Deliberately harming gulls is a criminal offence.
Demolishing the buildings where they nest is impractical and risks dispersing them to neighbouring towns, where they establish new nesting colonies.
Rather than viewing them as a nuisance, Rock recommends we learn from them instead: gull-inspired drones could help to deliver essential supplies in disaster-hit cities, where erratic wind currents make it difficult for conventional drones to fly. Watching gulls could have an additional benefit: tests in Cornish towns have suggested that gulls are less inclined to try to steal your food if you make direct eye contact with them. Rock also points at them and tells them to stop being silly.
There aren’t many strategies that can deter a determined gull, but apparently staring into their peculiar eyes really weirds them out.