They are masters of intimidation who stalk their victims relentlessly and without mercy.

They even started menacing motorists at a shopping centre.

In scenes similar to Alfred Hitchcock's 1963 thriller The Birds, hundreds of seagulls would gather at the Priory Meadow mall in Hastings.

They would swoop over the rooftop car park, pick their spot and drop a sticky payload of guano - bird mess to you and me - on the unsuspecting shoppers below.

Exasperated centre managers had tried everything to get rid of the gulls.

But a flock of robotic falcons, spikes and even a real eagle owl would not deter the birds.

The staff could take the intimidation no more.

They hired a "sonic scarecrow", an electronic device with a mercenary streak and a dislike for birds which screech and eat rubbish.

With a predatory squawk at the car park the device has single-wingedly eradicated the seagull scourge.

John Hough, centre manager, said pigeons were initially a nuisance in and around the shopping centre but seagulls became interested a new multi-million pound extension was added to the car park.

He said: "I don't think there's anything we haven't tried but we'd never had a problem at the car park until we expanded it last year.

"Then the majority of it we couldn't use because it was covered in seagull guano.

"We were bombarded. We couldn't have people treading on it, it could have been quite dangerous and to clean it off was a monumental task."

A flock of robo-falcons were installed three years ago to stand guard at the centre.

The squad of squawking machines, which hop up and down and flutter their wings, deterred nesting birds who used to swoop through the mall.

But outside the problems remained, with Kali the Bengal Eagle Owl recruited to join the fight.

And two new floors added to the car park just compounded the problems.

Mr Hough said: "The robo-falcons worked well in the mall - we've got one guarding each entrance. The pigeons used to rest in the rafters but they don't now because of the robot birds.

"Still, externally they didn't do the trick, so now we've turned to this new device, which emits distress calls intermittently that the birds find upsetting.

"The seagulls can be very aggressive when they're nesting and there were loads of them.

"We had designed in loads of anti-pigeon devices to the car park as it was, with netting and spikes, but after all that hassle with pigeons we suddenly had to deal with seagulls.

"You couldn't walk on it without slipping around all over the place. It was disgusting."

Contrary to the popular belief seagulls are thriving, they are actually an endangered species.

The RSPB has placed them on the amber list of birds because their numbers have dropped by 40 per cent since 1979.

The RSPB believes many seagulls - which live for up to 20 years and have wingspans of about 4ft - have entirely given up living on water. A survey in 1971 found there were no seagulls nesting on rooftops in Brighton and Hove.

By 2001 there were 235 pairs in Brighton and 261 in Hove and Portslade.

Experts agree that highrise flats - doubling as clifftops - and litter have created the perfect habitat.

Priory Meadow is spending £10,000 a year battling birds. The new sonic scarecrow has been designed by Uckfield-based Scarecrow Bio-Acoustic Systems.

Steven Ball, operations manager at the shopping centre, said: "We had a very serious problem, it seemed the entire bird population across the south coast chose to roost in the car park, it was astounding."

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