The Manx Shearwater summers on Observatory Island

The Manx shearwater, believed to be around 53 years old, was first tagged on 17 July 1953. It was found again on 21 June 2003.

The small black and white gull-like bird was found on Mew Island, next to Copeland Island off the north County Down coast.

Neville McKee of Copeland Bird Observatory said ornithologists were "really pleased" about the discovery.

"Manx shearwaters are strange birds," he said.

"They only come in at night during the dark hours. They nest in burrows under the ground.

"You almost never see their eggs - their chicks come out in September and off they fly.

"The whole breeding season is very long, about six months."

Mr McKee said that the birds were known to have a long lifespan, but this find was special.

We catch them regularly and routinely at night and they are quite used to us now Neville McKee Copeland Bird Observatory

"This bird is at least 50 years old, because when we ringed it, it was an adult.

"It could well be three or four more years older than that."

Ornithologists working on the islands are conducting a scientific study into the dynamics of the Manx shearwater population on the island.

"We have several birds that are over 40," Mr McKee said.

"We catch them regularly and routinely at night and they are quite used to us now.

"We would have handled a bird which was 40 years old about 15 or 20 times."

Other birds such as ostriches, emus and albatrosses have been known to reach a ripe old age.