On all the islands I’ve visited during my trip through the Atlantic Ocean, human-introduced predators are a big problem. Rats, mice, cats, they all arrived with ships and spread over the islands killing a lot if the native avifauna. Birds on those remote islands are not used to having mammalian predators around. Where it might be somewhat easy for a bird to get stuck on an island like that as they can fly across the ocean, for land mammals the sea is too big a barrier. Until humans gave a helping hand an, knowingly or unknowingly, introduced mammals on the islands.
Nowadays there are strict biosecurity regulations for visitors to these islands. Some islands, like Gough, are completely off-limits, while for others, like South Georgia, one has to go through a strict biosecurity protocol. All this to avoid introducing more alien species (mainly plants actually, but also rats and mice). This leaves the problem of the animals that have already established themselves on the islands.
On South Georgia, the rats had only colonised the mainland. But fortunately for the conservationists, glaciers divided the island into smaller ‘islands’, smaller patches where the rats were stuck. So the set of on a massive project to clear the island of rats, patch by patch. By now they are in the final stage of checking whether they have been successful and all rats have left the island (dead). Next year, they will even bring dogs to sniff for more rats. But it looks very hopeful. We already see a steep increase in the numbers of the endemic South Georgia Pipit, a bird that had suffered a lot from the rats and was confined to small islands in front of the coast. Even a few years into the project, we could already see them start recolonising the mainland. Great to see those little birds back on the places where they belong!
EDIT 09-05-2018: And the day after I write this blog, the following news is announced: South Georgia is officially declared Rat Free! Great news of course and a big compliment to all involved in this. Click here for the official news announcement by the South Georgia Heritage Trust.