Puffin numbers on one of Britain’s most important seabird colonies may be hit by the terrible summer weather, wildlife experts have warned. Flooded burrows on the Farne Islands off the Northumberland coast have been blamed for a serious drop in the number of fledged puffin chicks this year.

Each year National Trust rangers monitor 100 burrows with eggs on the islands and last year found 92 birds had fledged, seen as a remarkable success. But this year only about 50 successfully fledged chicks, known as pufflings, were found in the 100 burrows checked.

Ed Tooth, a ranger who lives on the islands, said: “We have had some freak downpours and storms. The drainage on some of the islands means that when you get really heavy rain, it floods the burrows out, and productivity has been quite low.”

Every five years the trust carries out a larger audit – the last was in 2013, when puffin numbers on the islands were strong, at just under 40,000 pairs. That was an increase on the 2008 figure, when a stormy summer hit numbers hard from a high of more than 50,000 down to 36,000 breeding pairs.

This month marks the 90th anniversary of the Farne Islands, once home to St Cuthbert, coming under the control of the National Trust. Since then they have become what the trust describes as a “jewel in its wildlife crown”, with more than 23 types of breeding seabirds living there, as well as one of the largest colonies of Atlantic grey seals in the UK.