The National Trust for Scotland’s Seabirds Recovery Programme: proposed brown rat eradication from the Inner Hebridean Islands of Canna and Sanday

The islands of Canna and Sunday are situated off the west coast of Scotland within the Inner Hebridean archipelago. The island of Canna is the largest being 5 mile long by 2 mile wide and Sunday 1½ mile long by ½ mile wide. The islands (excluding all inbye land) were designated an SSSI in 1987 and an SPA in 1997 for their seabird and raptor populations, particularly Manx Shearwater Puffinus puffinus, Shag Phalacrocorax aristotelis and White-tailed Eagle Haliaetuus albicilla. Studies carried out by The Highland Ringing Group have highlighted declines in several species of seabirds. The National Trust for Scotland in conjunction with the Highland Ringing Group investigated the cause of decline and brown rat was suspected to he the main cause. Some remedial work was carried out in 1997-1999 to prevent Manx Shearwater declining further but this species became extinct in 2000. Plans for a full rat eradication program were initiated in 1997 for the islands of Canna and Sunday and research into the environmental impact on other species for such a program were undertaken. A small mammal survey took place 1997-1999 since little was known on this group’s status. Studies found that there were few species on the islands and that numbers were low. It was found that Wood Mouse Apodemus sylvaticus had an interesting physiology and that further work would be needed to establish if this was genetically different from mainland species. However, this added to the project where this species had to be protected and samples are now in quarantine in Edinburgh Zoo until the eradication program has been completed. A rat distribution survey was carried out in the winter of 2000-2001 to determine their location and rough densities. There are several raptor species on the island and most do scavenge rabbits and rats which will be affected by poisoning. Though secondary poisoning in raptors using a 1st generation poison is unlikely, these risks had to be reduced to an acceptable level. A steering group was set up in 2003 to carry the project forward. LIFE-Nature fund application was made to Brussels and the Trust has now received full funding for the project.