The puffin population off Scotland's east coast has dropped by nearly a third in less than five years, prompting scientists to issue warnings about the orange-beaked seabird's future.
Puffin numbers in the Firth of Forth estuary close to Edinburgh have plummeted by 30 percent in the last five years.
Many of the round-bodied birds are likely to have starved in their winter feeding grounds as climate change reduces the plankton available in the North Sea, said Mike Harris of Britain's Center for Ecology and Hydrology.
"It is clear there is a widespread problem across Europe that is impacting on the population," he said.
The birds returning from the winter feeding grounds were fewer in number this year and many were not the weight they should be, Harris said. The puffins' main breeding ground is the Isle of May off the Scottish coast.
Other factors may have also played a role in the population decline, and more study is needed, Harris said.
The team first recorded puffin populations in 1975 when it found 2,000 breeding pairs by counting the number of nests in burrows on the island. The population had risen to 69,000 pairs by 2003 and scientists had expected 100,000 this year.
But the count in April came up with 41,000 pairs.
"We still have the largest population in Britain here on the Isle of May, so it's not all doom and despair. I don't think they are about to become extinct. However, we are keeping a close eye on this," Harris said.
Puffins are faithful to one breeding partner and always return to the same nesting site.
The puffins are not the only species to be affected by declining food stocks. Populations of small seabirds such as the guillemot and kittywakes have also been hit, said the Royal Society for the Protection of Birds Scotland.
Society spokesman Davey Fitch said puffins "are quite adaptable and can find food from a number of sources. Overall, this is a worrying trend as there is something potentially wrong with the supplies of food on the east coast of Scotland."