Scottish island declared rat-free after 3 year rat eradication programme

June 2008. Canna, the National Trust for Scotland's island property, will be officially declared rat-free during a visit by Environment Minister Mike Russell.

The last confirmed rat sighting was in February 2006. Now that two years have passed since that last sighting, the island can officially be labelled rat-free.

Environment Minister Mike Russell said: "Rats, while being fairly innocuous creatures in their natural environment, can have a devastating impact in a fragile ecosystem such as that of Canna. I am delighted to see the island declared officially rat-free and look forward to seeing its seabird population flourish."

Richard Luxmoore, Senior Nature Conservation Adviser with the Trust, said: Canna is such an important habitat for seabirds in Scotland that we simply had to act to protect this important site and give our seabirds every chance to thrive. Seabirds face so many threats from nature and man and need our help and protection. As a conservation charity, we had to remove the threat of predation from rats which we hope will boost bird numbers in the long term. The seabirds are being monitored over this summer to see just what impact our efforts have had, but already things are looking good. We have already had the first recorded breeding of Manx shearwaters for over ten years."

Bird populations under threat
The project to protect Canna's internationally important seabird colonies began in 2005, after several years of research by the conservation charity which decided it must act to prevent the decline of bird populations. Rats were eating the eggs and chicks of ground-nesting seabirds and this was seriously affecting their numbers.

10,000 rats
The island's entire rat population, estimated to have been up to 10,000, was trapped and poisoned throughout the project, using specialist knowledge of New Zealand experts, Trust staff and a large team of volunteers.

Wax blocks, impregnated with poison, were used to kill the rats in 4,200 bait stations set up across the island. Each station was checked twice a week. Two years of intensive monitoring has now confirmed that every last rat is dead.

Canna mice
During the work to eradicate rats, steps also had to be taken to preserve a population of distinctive Canna fieldmice. Project partners, Royal Zoological Society of Scotland (RZSS) captured and kept a population of mice at Edinburgh Zoo and Highland Wildlife Park for the duration of the project. Their studies have shown that the mouse population has returned to thriving condition since the project.

The project to protect Canna's seabirds cost less than its estimated £500,000 and was funded by the European LIFE Nature fund, Scottish Natural Heritage and the National Trust for Scotland.

Razorbills, shags and shearwaters

A survey carried out by the Highland Ringing Group shows that the number of key species, especially shags, razorbills and Manx shearwaters, appears to be on the road to recovery.

Razorbills, which nest amongst boulders and are especially vulnerable to rat predation, have shown a ten fold increase from just 27 successful nests in 2005 to 273 in 2007. This reverses a long-term decline which saw numbers decline from 440 in 1995.

Shags were also badly hit but, at one colony, numbers are up from just 48 pairs in 2005 to 72 pairs in 2007. More importantly, the average number of chicks successfully reared is up from 0.7 per nest to 1.2.

Canna used to be the home for one of the largest colonies of shags anywhere in Europe but numbers had declined by over 40%. The first nests to suffer were those in accessible boulder fields around Garrisdale, the Nunnery and Lamasgor (areas of Canna), with the birds retreating to the more inaccessible ledges. Recovery in the boulder fields has been particularly noticeable.

The Manx shearwater colony, estimtaed to have been as large as 1500 pairs, was completely destroyed. The use of tape recordings of Manx shearwater calls revealed that birds have come back to some of the burrows of the former colony, last used in 1999, and that other birds may be present around the island.

Abbie Patterson, National Species Recovery Officer at the NTS, said: 'While it will take a long time for seabird numbers to build back up to their previous levels, it is encouraging to see that the long term decline has been halted and that numbers of vulnerable species have begun to increase once more.' Canna is owned by the National Trust for Scotland. Research showed that a rise in Brown rat numbers, probably due to milder winters, led to a sharp increase in predation on the island's seabirds.