THEY swoop with speed and ferocity, arriving like a rocket-propelled dart at up to 140mph.

They are the curse of pigeons and other small birds, but town centre managers love them as they keep the “flying rats” at bay.

Now they’re enjoying party time in the county of Suffolk as new nesting sites are being surveyed every year.

They are peregrine falcons – and their success is delighting wildlife experts in the county.

But life isn’t all plain sailing even if you are at the top of the food chain!

It’s now five years since the first peregrine falcons nested in the county for 200 years as a pair set up home under the Orwell Bridge. Since then they have stretched their wings to other parts of Suffolk.

A pair tried to built a nest on a disused crane at Landguard in Felixstowe earlier this year – but their plans were thwarted by an aggressive female hybrid who saw off a young female and is believed to have killed a juvenile that had flown over from Antwerp in Belgium.

And another escaped hybrid is responsible for keeping peregrines away from a potential penthouse roost in the heart of Ipswich.

Meanwhile the Orwell Bridge pair have continued to thrive and have raised more youngsters this year.

A young male born at the bridge a few years ago has now set up home with a female at Lowestoft, and a pair have been seen sizing up a potential roost at Sizewell on the Suffolk coast.

Steve Piotrowski, from the Suffolk Ornithologists Group, said: “The peregrines are spreading in Suffolk after they first appeared at the Orwell Bridge in 2007 – and that is very good news.

“It’s not always that straightforward as we saw in Felixstowe this year.

“There is a problem with hybrid birds that have escaped from falconers. There is a very large bird that has moved into a box at the top of The Mill and that keeps peregrines away.

“It is a gyr falcon/saker falcon/peregrine hybrid that was used to scare birds away from the Foxhall Tip until it escaped a couple of years ago.”

The ornithologists had been trying to persuade its owner to do more to try to recapture it which should allow peregrines to move in.

“Having peregrines move in is good for towns because it helps to control feral pigeons – developers and town planners like to encourage them. Hopefully we will see many more peregrines in future years,” said Mr Piotrowski.

n Are you happy to see peregrines become established? Or do you worry about the impact on other birds? Write to Your Letters, Ipswich Star, 30 Lower Brook Street, Ipswich, IP4 1AN, or e-mail starletters@archant.co.uk