Scientists are gluing tags to puffins to try and figure out why their numbers are dropping.
Puffin numbers had been rising over the last few years, but last year showed a sudden sharp drop.
So researchers on the UK's biggest puffin colony, the Farne islands, are gluing little recording devices to the birds to track where they go.
It's hoped that information can be used to figure out what it might be that's causing their decline.
Their teeth point backwards
They're only about 30 cms tall
A baby puffin is called a puffling
Their bills can hold lots of fish
In a 2003 survey of puffins on the Farne Islands, 55,674 were counted.
But in 2008 that had dropped to 36,500.
"These devices are important for the out-of-breeding season because we know very little about what the birds are doing," said Dr Richard Bevan, a bird expert.
"We have got an idea that they are spending their time out in the North Sea, but are they? How much time are they spending out there? Where are they going? "
Because female puffins lay only one egg a year, if lots of adults die over a few years, it can badly hit the population.