Ananova:

Puffins are to be fitted with satellite transmitters for the first time in an effort to understand a worrying decline in their numbers in the last five years.

Scientists are to fit tiny global positioning system (GPS) devices to the sea birds' legs to work out what is happening to them, reports the Daily Telegraph.

Possible reasons include climate change causing sand eels, puffins' main food source, to move north. Pollution can also affect numbers and competition from other species such as gulls.

Puffins on the Farne Islands will be fitted with GPS this summer. When the data is collected from returning puffins the following year it will provide clues to the kind of feeding grounds the birds have been to and the threats they are exposed to.

David Steel, National Trust Head Warden on the Farne Islands, said puffins were breeding successfully so it was essential to find out what could be causing the death of the birds out at sea.

"This has become the case of the disappearing puffins," he said.

Puffins spend the winters at sea, floating, swimming and diving for food, coming to land only during the nesting season.

Dr Richard Bevan, of Newcastle University where the data will be processed, said scientists will be able to work out why puffin are dying from seeing where the birds go in the winter.

"Technological developments now mean that we're getting closer to finding the pieces of the jigsaw to help solve the puffin puzzle. The new data will help explain what the puffins are doing when they're on the Farne Islands and hopefully then help us to understand why numbers have declined so dramatically," he said.

On the Isle of May in the North Sea, the largest breeding colony in Britain, numbers fell from 70,000 in 2003 to 41,000 in 2008. On the Farne Islands numbers dropped from 56,000 to 36,000.