The seabird populations on Canna have been studied since 1969 by volunteer members of the Highland Ringing Group. During the 1970s and 1980s many species, particularly shags, auks and gulls under went large increases in breeding numbers, with the shag colony becoming one of the largest in Europe. Numbers were so high that the island was declared a Special Protection Area (SPA) for its seabirds, part of the European Union Natura 2000 network of protected sites.

In the late 1980s and through much of the 1990s seabird numbers began to decline. Research by the Highland Ringing Group and the National Trust for Scotland showed that high levels of predation by introduced brown rats (Rattus norvegicus) were affecting seabird breeding success and resulting in the birds abandoning traditional breeding areas on the island.

  Predated guillemot egg   

A three-year project is underway to secure the recovery of the internationally important seabird colonies on Canna by eradicating rats from the islands. Funding has been provided by the EU LIFE Nature programme with additional support from Scottish Natural Heritage, and the Royal Zoological Society of Scotland.