Experts have been left baffled by a dramatic fall in puffin numbers over the last five years, and what factors have contributed to their decline.

A survey of the breeding pairs of puffins carried out on eight of the Farne Islands in the summer of 2008 found that numbers were down by one third compared to the previous survey in 2003.

But new research is now under way on Brownsman Island, off the Northumberland coast from Seahouses, where the region's iconic puffins settle to roost over the early summer months.

They are being tagged with global positioning satellite (GPS) transmitters – a world first for these birds – in order to shed new light on puffin movement and behaviour.

The tags, which are glued onto the birds' feathers and fall off after several days, will help map their movements to find out where they go to fish, how they get there and what they do on arrival.

David Steel, National Trust Head Warden on the Farne Islands, said: "This has become the case of the disappearing puffins. Young puffins are successfully fledging each year and it would seem that their staple food, the sand eel is in good supply, but they're just not coming back to the islands.
"This research, including further counts, is designed to shed some light on what is happening."

A team of researchers from Newcastle University is now working with the wardens on Brownsman, where they are tagging and ringing puffins with assistance from the Natural History Society of Northumbria.

In mid July, before the puffins depart the islands for winter, geolocators will be attached to a leg ring on some of the birds.
When the data is collected from any returning puffins the following year it will provide an outline of the birds' movements while they wintered at sea.

Dr Richard Bevan, of Newcastle University, said: "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."

Further work is also being carried out using time-depth recorders, which provide information on the puffins' diving behaviour, such as how often they dive and how deep, as well as sea temperatures.

This information may help understand how puffins might be affected by climate change and changes in sea temperatures.