About 100 kilometers south of Cape Horn, the southernmost point of South America, lie the one-square-kilometer Diego Ramírez Islands. They are home to the Subantarctic rayadito (Aphrastura subantarctica), which until recently was thought to be the thorn-tailed rayadito (Aphrastura spinicauda), a species widespread in Chile and adjacent regions.
A clue that these were different bird species came from the completely different habitats in which they occur. While the thorn-tailed rayadito exclusively inhabits dense forest undergrowth, there are neither trees nor bushes on the Diego Ramírez Islands that the birds could inhabit.
Ricardo Rozzi from the Universidad de Magallanes and his team spent several years measuring the rayaditos living on the Diego Ramírez Islands: all the birds were larger and heavier, with shorter tails and more robust bills than their mainland relatives. The birds also show behavioral differences. Since there are no trees, the rayaditos of the Diego Ramírez archipelago nest in ground burrows; they also fly only short distances. Ultimately, Rozzi and his team were able to use genetic studies to demonstrate that the two bird species are clearly distinct from each other, and in August 2022 they published the first scientific description of the Subantarctic rayadito.
In geologically recent times, no exchange between the thorn-tailed rayadito and the Subantarctic rayadito could have taken place. This is due to the Drake Passage with its strong westerly winds and ocean currents, which separates the Chilean mainland from the Diego Ramírez archipelago. How the Subantarctic rayaditos originally reached the archipelago is not entirely clear, but they were fortunate, as the islands were difficult for seafarers to reach and not interesting enough for rats, goats, mink, or similar animals to be introduced—species that are known to have caused the extinction of many island-endemic bird species, such as the Stephens Island wren, the Saint Helena rail, or the white-chested white-eye.
About the author: Doreen Fräßdorf
Doreen Fräßdorf is the author and publisher of artensterben.de. She researches and writes about extinct and endangered species in the modern era, with a focus on red lists, scientific studies, historical sources, and current conservation efforts. The goal is a clear, evidence-based overview of biodiversity loss and species protection.
She is also the author of a non-fiction book about extinct modern-era mammals.
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