One of the world’s rarest seabirds has nested on Bermuda again after a gap of nearly 170 years, an environmental organisation said yesterday.

The Audubon Society said a pair of roseate terns (Sterna dougallii) built a nest on a small nature reserve islet in the Hamilton Harbour/Great Sound area and hatched a single egg last month. David Wingate, former conservation officer, said: “Out of concern for the safety of the birds and the egg/chick, it was decided to keep the exciting news quiet until the chick had fledged.”

Dr Wingate added the chick hatched on July 24 and was double-banded and DNA tested.

He said it had now fledged and would probably head south to spend the winter with its parents off Brazil.

Dr Wingate added: “It is highly likely that the same pair will return to nest again next year, but the chick, which we nicknamed Phoenix, will take at least three years to mature.”

The pair were spotted in Hamilton Harbour in May by Dr Wingate and Miguel Mejias.

The roseate tern was once common in Bermuda, but was wiped out by scientific collectors and hunters in the 1800s.

The last nests were reported on Gurnett Rock at the entrance to Castle Harbour in the East End in the 1840s.

The island still has a small population of the common tern — Sterna hirundo — but numbers have suffered a major decline because of hurricane strikes during the nesting season.

Dr Wingate said: “One encouraging fact about the roseate tern recolonisation is that they are much better adapted than the common terns to survive hurricanes and largely replace the latter in the hurricane belt, notably in the Bahamas and the Antilles.”

He added the roseate tern was more common in Bermuda in the 19th century than the common tern, before they were collected and hunted to extinction on the island.

Dr Wingate said a single roseate tern joined the common tern colony on the island over the last two years and began courting. He added: “This year that bird brought a mate of its own species with it and the rest is history.”