Rats: what are they good for? Well, if you ask any puffin, they’ll tell you: “absolutely nothing.”

The island of Lundy off the southwest coast of the UK had a rat problem that would rival a dodgy New York pizza shop. But now, following the success of a huge conservation project, the invasive rodents are no more, sparking an unprecedented resurgence of the island’s seabirds.

The Royal Society for the Protection of Birds, who led the project, says the population of seabirds on the island has tripled to 21,000 birds since rats were eradicated in 2006. The number of Manx shearwaters has grown from 297 pairs to 5,504, while the beloved Atlantic puffin population has boomed from just 13 birds to 375. The island is also witnessing an encouraging renaissance of guillemots and razorbills.

Try not to feel too sorry for the rodents that have been kicked off the island. The rats are an invasive species that only arrived on Lundy during the 20th century by hitching rides on merchant ships. These new-comers are also pretty unpleasant to the island’s natives.

"Invasive species damage island ecosystems in many ways – everything from eating seabird adults, chicks, and eggs directly, to changing plant and invertebrate communities," Dr Alex Bond, Senior Curator in Charge of Birds at the Natural History Museum, who was not directly involved with this research, told IFLScience. "Seabirds evolved to breed in places without predators, like islands and steep cliffs, so when species like rats or mice or cats are introduced to an island, the birds just don’t have the behavioral tools to respond." 

“Introduced mammals, particularly rodents, are a huge problem for seabirds worldwide," Dr Bond added. "There are hundreds of invaded islands that harbor huge amounts of biodiversity, much of it found nowhere else in the world. Across the >350 species of seabirds globally, introduced predators are the single biggest threat."

The Atlantic puffin is classified as vulnerable to extinction, according to the IUCN Red List. They can be found across the Atlantic Ocean in the Northern Hemisphere, but their global population numbers are slipping, primarily due to pollution, climate change, and invasive species.

While they might not have quite the same cult following as puffins, Manx shearwaters are also incredibly important seabirds across much of the Atlantic Ocean. The birds are sometimes known as “daredevils” due to their acrobatic flying techniques, diving so close to the water’s surface that their wings almost dip in. 

“It is exciting to see this level of recovery in Manx shearwaters, one of our most important seabirds,” Dean Jones, Lundy Warden, said in a statement. “In spring, the island comes alive at night with the sound of these amazing birds. The increase in puffins, guillemots and razorbills is also very encouraging for the future of seabirds on Lundy and we are maintaining our vigilance to ensure rats cannot return to the island.”