The trials and tribulations of one of Britain’s largest colonies of terns have been captured for a BBC wildlife programme tonight.

The 1,300 pairs of terns – or sea swallows – at Cemlyn nature reserve were filmed over a breeding season for The Nature of Britain programme.

The birds travel thousands of miles from Africa to Anglesey because of the good fish stocks in the sea there.

The programme can be seen on BBC1 at 2100 GMT on Wednesday.

Cemlyn is run by North Wales Wildlife Trust (NWWT) and is in an Area of Outstanding Natural Beauty.

The area is ideal for breeding terns because of the availability of sand eels and small fish, according to John Rowe from NWWT.

“This is the only colony in Wales and it is to do with fish stocks in the surrounding sea,” he said.

The reserve is situated on the north coast of Anglesey, three miles from Cemaes on land owned by the National Trust but leased to the NWWT since 1971.

It includes a large lagoon, separated from the sea by a naturally created shingle ridge known as Esgair Gemlyn.

The birds attract tourists to the area with 3,000 visitors recorded last year.

Over the birds breeding season – after their flight back to Anglesey from Senegal in Africa – the cameras followed the ups and downs in the colony.

“We have mostly sandwich terns, but also common terns and arctic terns breeding here,” added Mr Rowe.

“What I like most about them is all the troubles they have to deal with.

“They fly so far, breed in such big numbers close together, they deal with a lot.”

Viewing the birds close up on the ground is usually quite difficult as they like to keep their distance, so the TV cameras will provide and opportunity to see them close up, he added.