A kaleidoscope of shifting shapes has been entertaining townsfolk across Great Yarmouth.

As night swallows day a great whirl of starlings has been swooping over some of the town's most prominent buildings.

The evening routine - known as a murmuration - sees hundreds, possibly thousands, of birds flying across the sky in what looks like a co-ordinated display worthy of any of the town's theatre stages.

However, there may be just a few more weeks left to see them perform as the majority of the birds head back to Europe and Russia to breed.

Paul Stancliffe, ornithologist at the British Trust for Ornithology based in Thetford, said each bird kept a close eye on five or six of its neighbours creating great waves of movement within the flock.

The phenomenon always occurred at dusk just as the birds were looking to roost.

"At its very basic it's safety in numbers," Mr Stancliffe said.

"Just before they go to roost they gather in groups, but not one of them wants to be the first into the roost because there might be something in there that might nab them, and they do not want to be the last either.

"There is a lot of nervousness around.

"That is why they are constantly moving.

"They do that by looking at each other. Five or six birds will watch each other very closely."

Despite their apparent numbers Mr Stancliffe said starlings were in decline with the UK having lost some 75pc of its breeding population.

Most of those flocking were from mainland Europe and would start to head back at the end of the month meaning the murmurations would start breaking up.

The birds like a bit of cover from the wind and rain at night and head for thick foliage that will accommodate a lot of individuals, like leylandii hedges.

They also use their time together to exchange information about feeding spots, Mr Stancliffe said, adding: "You do not need a massive amount to enjoy a murmuration, but as soon as they start thinking about breeding they will be off."