Scientists have found a new fossil of an owl species that lived 2,000 years ago in the remote São Miguel Island off Portugal. It was likely wiped out by the arrival of human settlers in the archipelago in the 1400s.

Scientists were digging in a cave near the volcano Água de pau when they found the bones of the bird. They put the bones together like a jigsaw to figure out what the bird must have looked like.

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The species, christened the São Miguel scops owl (Otus frutuosoi), adds a new species to the Otus family of owls, commonly known as scops owls. The tarsi bones of the São Miguel scops, its stick-like connections between the thighs and feet, were weak. Coupled with short wings, the owls were likely not great fliers, but rather lived on the floor of the island’s laurel forests eating insects. The work was published in the journal Zootaxa.

It was possible for the birds to live on or close to the ground because there would have been few predators on the island 2,000 years ago.

The São Miguel Island is part of the Azores Islands archipelago, located about 900 miles west of Portugal. These are volcanic islands that jut out of the ocean floor at the tectonic triple juncture where the North American Plate separates from the Eurasian Plate and the African Plate along the mid-Atlantic ridge.

At the beginning, São Miguel Island was nothing more than rock.

Over time, a very few plants, insects and birds would have crossed the ocean by chance and stumbled onto the Azores. And they would have found it difficult to fly back, given the vast ocean separating the island from the main land. The immigrant birds would have instead adapted to their new home. Over time, they would occupy niches and evolve into new species of birds unique to the island – such as a flightless owl species that feeds on insects.

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Given its remoteness and size, the Azores Islands should have many endemic bird species, but it has only two. Compare that against the Madeira Islands, which has four, the Canary Islands, which has five endemic bird species, and Cape Verde which has six. Scientists have suggested that the Azores had more species that then died out.

The São Miguel scops owl, which is the first fossil discovered on the island of an extinct bird species, suggests this might be true.

The trigger of extinction is likely to be humans, the scientists suggest. That’s not an unreasonable claim given that most volcanic islands witnessed rapid extinctions once mariners took to the oceans.

Mariners settled on the Azores Islands in the 15th-century. The impact of their arrival can be indirectly surmised by examining the historical record of the nearby Canary and Madeira Islands. There, human settlers caused extinctions of a number of bird species, by hunting, introducing new species that would compete for resources, and by changing ecosystems.

It is likely the mariners introduced mammals to the Azores, including the mouse. Given that the scops owl lived on or close the ground, mammals could have become predators, eating the eggs and fledglings of the birds. Mammals could have also competed directly with the owls for food.

Photo: Otus scops owl perched on a branch. (Peter Johnson/Corbis)

Rendering of the São Miguel scops owl, which is related to the Eurasian scops owl (Otus scops). Credit: J. A. Peñas