Weighing just 0.035 pounds (16 grams), it’s understandable why the Subantarctic rayadito has only just been discovered. Scientists recently discovered the species on the Diego Ramírez Islands, off the southern tip of South America.
The species is small with brown, black, and dark yellow feathers. But one of its most interesting features is the bird’s beak, which is large for the bird’s size despite the species being found in a grassy area without trees.
“There are no bushes and no woodland species, literally in the middle of the ocean a forest bird has managed to survive,” said Ricardo Rozzi, an author of the study from Chile’s University of Magallanes and the University of North Texas and the director of the Cape Horn International Center for Global Change Studies and Biocultural Conservation (CHIC).
The discovery, published in the journal Nature, has led scientists on a six-year-long investigation as they analyzed the appearance and behaviors of the species, which varies from other rayadito species.
The researchers analyzed 13 of the Subantarctic rayadito birds and compared them with other adult rayaditos (Aphrastura), including 50 from the NW Beagle Channel and Navarino Island, finding that the birds found on Diego Ramírez Islands differed from the others.
“Birds from the Diego Ramírez population were significantly heavier and larger (with a longer and wider bill and longer tarsi), but they had a significantly shorter tail than birds from the other two populations,” the study reported. “The PCA analysis shows that the Aphrastura populations of the Beagle Channel and Navarino Island overlap in body dimensions, whereas the individuals of the Diego Ramírez population form a clearly separate cluster.”
The differences could be attributed to “island syndrome,” the scientists said in the study, where small birds likely evolve to increase in size to better withstand pressures from limited food sources and predators. The shorter tails may have evolved for easier movement among the landscape of Diego Ramírez Islands.
“On Diego Ramírez, restricted movement within a more sheltered habitat, close to the ground level, may have driven selection for shorter tails that may facilitate moving among dense tussock,” the study explained. “Shorter tails could also have arisen through genetic drift after a small number of birds reached the archipelago or because other selective pressures for longer tails might have been relaxed in the environmental conditions of Diego Ramírez.”
The study authors hope the newly discovered species can give more insight into biodiversity of the Diego Ramírez Islands, but they also warn that this small bird will need protections against extinction from rats, domesticated cats or American minks, which have become problems on other subantarctic islands.
The study concluded, “Because of the small size of the Diego Ramírez islands and the potential arrival of exotic mammal predators, it is pressing to protect this new endemic species from extinction.”
This article by Paige Bennett was first published by EcoWatch on 1 September 2022. Lead Image: The’ Rayadito Subantartico’ (Aphrastura subantarctica), is seen at Gonzalo island. Universidad de Magallanes-Centro Internacional Cabo de Hornos.
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