Puffins left Ramsey Island over a hundred years ago, when rats from a sinking ship infested it.
The rats destroyed the puffins' nests and ate their eggs, so the puffins flew away from the island west of Wales.
But now the rats have gone and the RSPB is using a special sound system to try to get the birds to return.
The solar-powered sound system plays a recording of the puffins' call on a loop.
Nel visited Ramsey Island to find out more.