Swallowtail butterfly reappears on Bornholm, Denmark, after decades of absence

The swallowtail butterfly, once thought extinct in Denmark since 1978, has made a surprising reappearance on the island of Bornholm. In early July, a local gardener, Arne Jegind, spotted a large and beautiful butterfly resting on his bronze fennel. Suspecting it might have escaped from a nearby butterfly park, he was astonished when he learned that this butterfly was a swallowtail, which has traditionally only been seen as a migratory visitor to Denmark for nearly five decades.

This year, however, the swallowtail has been frequently sighted on Bornholm, reported over 20 times in various private gardens. At least 18 swallowtail larvae have also been discovered, a fact that excites local biologist Michael Stoltze. Stoltze notes that such a high number of sightings and larvae finds has not been recorded on the island in nearly a century.

Jegind’s garden stands out as a wildlife-friendly area, free from pesticides and featuring wild growth, which encourages butterfly populations. The increasing interest among Danes in cultivating wild gardens is evident; nearly 31,000 gardens have registered for the “Slip Haven Fri” initiative, aimed at letting at least 20% of garden space grow wild and avoiding chemical sprays.

Biologist Therese Nissen emphasizes the importance of individual efforts to combat biodiversity loss, highlighting that while gardens can create green refuges, broader natural habitats are crucial for the survival of species like the swallowtail. Professor Rasmus Ejrnæs from Aarhus University concurs, stating that more extensive natural areas need to be restored for the species to thrive permanently.

With the newfound presence of swallowtail larvae in Bornholm’s gardens, there is hope that this butterfly may establish a permanent summer residence, potentially reintroducing a species once thought lost.