There were 55,674 pairs in the Farne Islands in 2003, The Independent reported Saturday, and one-third fewer, 36,500, this year. The survey of eight of the islands was done by National Trust Wardens who found declines on all islands with the number down by more than half on four.

The Farnes are a group of rocky islands off the Northumberland coast known for their colonies of sea birds and grey seals.

David Steel said the problem appears to be puffins fledged on the islands are failing to return to breed, possibly because something is killing them early in life.

"The results from this survey have completely surprised us, as we were predicting another rise in the numbers of breeding pairs," Steel said. "Stocks of sand eels, the staple food of puffins in the summer, are in good supply around the islands and there is a lack of ground predators, creating a good environment for puffins to breed."