Scientists have described a new Rayadito species from remote sub-Antarctic islands off Chile’s southernmost point.
Rayaditos are small, long-tailed members of the stovebird family. Two species are currently recognized – thorn-tailed rayadito, widespread in temperate forests and subtropical dry shrubs south of 30°S in Chile and Argentina, and Masafuera rayadito, a rare bird native to Alejandro Selkirk Island on the Juan Fernández islands is endemic. They prefer heavily wooded areas, including forest edges, where they browse bark and moss surfaces for insect prey.
On the windswept and treeless islands of the Diego Ramírez Archipelago, about 110 km south of Cape Horn, an isolated Rayadito population has always stood out as unusual. Now, in a comprehensive new study, Ricardo Rozzi and his colleagues have presented evidence suggesting these birds deserve full species status.
The newly described sub-Antarctic rayadito inhabits islands devoid of forested vegetation and spends its life in dense clumps of grass (Rozzi et al.).
The research was conducted on three visits over a six-year period. The team caught 13 individuals with fog nets and found that Diego Ramírez’s rayaditos were significantly heavier and larger than their mainland counterparts, with a longer and broader beak and tarsi, and a significantly shorter tail.
In this forestless landscape they observed that the birds stayed in dense clumps of grass Poa flabellata, in whose stands there is a calmer and warmer microclimate. The paper states that individuals “typically made short and low flights and rarely moved above the cover of the grass tussock” and that most nest sites “consisted of burrows with individual entrances”, four of which were abandoned seabird nests and one of which was a natural ground cavity.
In addition, researchers found that Diego Ramírez’s Rayaditos were sufficiently distinct in their genetics from currently recognized species. Given the significant differences in the genetics, morphology and ecology of the Diego Ramírez birds, the team proposes that the new species be named Subantarctic Rayadito Aphrastura subantarctic.
In the open-access paper, the researchers further emphasize that protecting this new endemic species from extinction is of paramount importance, and point to the arrival of invasive predators such as rats, wildcats and American mink to other islands in the Cape Horn Biosphere Reserve that the Diego Ramírez Archipelago is kept predator-free.
Rozzi, R, Quilodrán, CS, Botero-Delgadillo, E and 14 others. The sub-Antarctic Rayadito (Aphrastura subantarctic), a new species of bird in the southernmost islands of the Americas. Scientific Reports. DOI: https://doi.org/10.1038/s41598-022-17985-4