A kittiwake colony is the Isles of Scilly has suffered a breeding failure
Kittiwakes have been disappearing from large stretches of the South West coastline, according to the RSPB.
The charity said two unsettled summers had had a big impact on numbers, particularly around Land's End.
The plankton which fish feed on has been further below the sea's surface because of the weather.
This has made it far more difficult for adult kittiwakes - which are not deep-diving birds - to find food for themselves and their chicks.
Tony Witehead from the RSPB said: "As well as hindering adults' ability to find food, when we have a cold, wet, windy summer like this year and last year, it really doesn't do the chicks any good because they're sitting on exposed, rocky ledges."
The RSPB said there had been a really worrying decline in the kittiwake population in other areas in the South West.
"On the Isles of Scilly there's been a complete breeding failure in the past three years," Helen Booker, also from the RSPB, told BBC News.
"Another colony where we had about 200 pairs two years ago has now been abandoned altogether because of a lack of breeding success."
Kittiwakes winter out at sea in the Atlantic and only come to shore in the spring and summer to nest and breed on cliff faces and other high places.