LONDON >> On a spring afternoon last year, Neil Fraser was walking down the main shopping street in Aberdeen, a port city in northeastern Scotland, when something strange happened. The bacon-and-chicken sandwich he was halfway through eating suddenly vanished from his hand.

The culprit? A hungry bird he hadn’t seen coming.

“The sea gull flew in from behind me,” Fraser, a manager at the Old Schoolhouse pub in the city, said by phone today. The bird knocked down his hand and, before he realized what was happening, it was all over: “The sandwich and the sea gull were both gone.”

Aggressive gulls trying to snatch people’s food, and at times succeeding, have been a long-standing nuisance in Britain, and various solutions have been proposed over the years, including not feeding the birds, holding a stick or umbrella overhead and installing wires on roofs that they use for nesting. The Old Schoolhouse pub even reportedly offered customers water pistols to deflect the birds.

Now, new research proposes a different approach: staring them down.

A study published in the journal Biology Letters today by the Royal Society, the world’s oldest continuous scientific society, suggested that making eye contact might be key to fending off herring gulls, a familiar sight in British seaside towns.

The study, conducted late last year in coastal towns in Cornwall, in southwestern England, focused on that species, which are white-, gray- and black-feathered, with beaks of yellow and red.

The researchers tried to test 74 birds by placing potato chips in front of an experimenter. Just 27 of the gulls bit the bait — a factor that the research team attributed to whether the experimenter was facing toward or away from the gull.

“Gulls took less time to approach when the experimenter was facing away versus looking directly at them,” wrote the research team, which was led by Madeleine Goumas, a postgraduate researcher at the University of Exeter. “This demonstrates that gulls use behavioral cues from humans when making foraging decisions in urban environments, and that they find human gaze aversive.”

The pattern appears to coincide with gulls’ tendency to use the element of surprise when preying on food.

The gulls see humans as large, potentially dangerous animals, Viola Ross-Smith, a spokeswoman for the British Trust for Ornithology, suggested in a phone interview Wednesday.

“They are more likely to surprise you; they are more likely to attack from behind,” Ross-Smith said, as was the case with Fraser and his sandwich — although she said that calling such incidents attacks would be an overstatement. “It can feel like an attack to a person,” she said, “but they are not really attacks, just a bird feeding.”

She added that such occurrences were not common.

“We can also see it in the study — only some birds would attempt to take food,” Ross-Smith said, although she added that the incidents were more likely during peak tourist season, when there were “lots of potential candidates they can take food from.”

While the number of herring gulls in urban areas has increased, the species’ overall population in Britain appears to be in decline, with about 139,000 breeding pairs remaining, according to the Royal Society for the Protection of Birds, the country’s largest nature conservation charity. There are also around 110,000 pairs of lesser black-billed gulls in Britain, it estimates.

The conservation charity also suggests a tactic for defending against any gulls that come close: move away, or raise your arms over your head. Waving your arms would agitate the birds, it advises.

There are legal restrictions on how gulls can be countered, however.

All gull species in Britain are protected under the Wildlife and Countryside Act 1981 and the Wildlife (Northern Ireland) Order 1985, making it illegal “to intentionally or, in Scotland and Northern Ireland, recklessly injure or kill any gull or damage or destroy an active nest or its contents,” the charity said on its website.

“However,” it added, “the law recognizes that in certain circumstances control measures may be necessary.”

In some cases, the charity said, licenses can be issued permitting the destruction of gull nests if no non-deadly solution is possible and if “it is done to prevent serious damage to agriculture, the spread of disease, to preserve public health and safety and air safety, or to conserve other wild birds.”

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