PUFFINS are once again rearing chicks on a landmark Scottish island, 15 years after a successful rat eradication programme.
Ailsa Craig, 16km off south-west Scotland, once offered a safe haven to hundreds of thousands of birds.
Nineteenth-century observers reported the sky around the island being "black with puffins" in summer, too numerous to count. But after rats infested the island, the puffins vanished and did not breed there for more than 80 years.
Dr Bernie Zonfrillo, who was involved in the rat removal, told The Scotsman: "We know for sure now that puffins have re-colonised the island, and at last I have held a puffin chick bred on Ailsa Craig in my hand."
At the end of the 19th century, rats swam ashore on then rat-free Ailsa Craig following a shipwreck close by.
The eggs and young of the defenceless seabirds provided the invaders with abundant food. The rats rapidly multiplied, and the seabirds rapidly declined. By the 1930s, the vast colony of puffins had disappeared completely.
A few abortive attempts at rat eradication in the early 20th century were to no avail. But in the early 1990s, a new project was organised by Glasgow University, support by Scottish Natural Heritage, RSPB and the Scottish Ornithologists Club, plus the Marquis of Ailsa and pest control firm Rentokill.
In autumn 1991, Royal Navy Search and Rescue Helicopters airlifted tons of humane rat poison on to the summit of the island. Areas where rats remained were identified using special sticks dipped in fat that the rats chewed, their teeth marks leaving tell-tale evidence. Back-up baiting was undertaken and, within three years, the rats were gone.
Young puffins began to hang around the island in the late 1990s. As numbers increased, they became bolder, being first seen exploring the ancestral puffin nesting areas on steep grassy slopes in 2002.
Puffins nest in deep burrows, making it difficult to know if they have bred or not. "Even though we saw puffins standing near burrow entrances, we couldn't be sure they had produced chicks," said Dr Zonfrillo.
Now The Scotsman can reveal that once again there is a puffin colony on Ailsa Craig. Over 200 puffins have been recorded ashore this season, and between 50 and 100 pairs are breeding.
Puffins can live up to 30 years in the wild, and produce a chick each year if conditions are good. Once adults, they return to their colony of birth to breed.
Ailsa Craig is a steep-sided volcanic plug, its granite much prized throughout the world for curling stones. It is also known as 'Paddy's Milestone' because of its landmark position in the sea-crossing from southern Scotland to Northern Ireland.
Anne McCall, RSPB Scotland regional director, said: "It is a real thrill, for everyone who loves Scottish wildlife, to have puffins back breeding on Ailsa where they belong."