The Inaccessible Island rail (Atlantisia rogersi) is the smallest flightless bird in the world. It has grey legs, a short, black bill, and red eyes. How they got to Inaccessible Island, a remote island in the middle of the South Atlantic, is a biological puzzle that has confused scientists for a century.

Less than a hundred years ago, many scientists believed that the bird species once went to the island by walking on land extensions which later disappeared into the depth of the ocean. Therefore the bird was given the Latin name Atlantisia. But in a new study conducted by biologist Martin Stervander along with researchers from Portugal and South Africa during his time at Lund University in Sweden, they found that the ancestors of the Inaccessible Island rail actually flew to the island from South America about 1.5 million years ago.

By analyzing DNA from the Inaccessible Island rail via modern sequencing techniques, researchers found that the black rail in North and South America and the Dot-winged crake in South America are the bird's closest now living relatives. It's proved by DNA that the ancestors of the Inaccessible Island rail actually came from South America. Since the bird has no natural enemies, its ability to fly has been lost through thousands of years of evolution.

According to Bengt Hansson, one of the researchers behind the study and a professor at Lund University, the discovery focuses on preventing enemies of the Inaccessible Island rail from being introduced on the island. If that happens, the bird might disappear.

Apart from alien species, diseases and natural disasters also post threats to the Inaccessible Island rail population. Currently, the bird has been classed as Vulnerable on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species since 1994. 

Several conservation measures have been proposed to protect the bird, including restricting access to the island on which the bird lives and research into the causes of the bird's mortality.