A six-week expedition to three small island groups near Sulawesi, Indonesia has yielded five new songbird species and five new subspecies.

The new species and subspecies were described in a paper published in Science last week. Frank Rheindt, a professor at the National University of Singapore, led the research team that made the discoveries using geological history and the notes of historical explorers as a guide in their search for new avian species.

While locals knew of some of the species already, it’s possible some of the birds had gone unnoticed because they sound more like insects.

A six-week expedition to three small island groups near Sulawesi, Indonesia has yielded five new songbird species and five new subspecies.

The new species and subspecies were described in a paper published in Science last week. Frank Rheindt, a professor at the National University of Singapore, led the research team that made the discoveries using geological history and the notes of historical explorers as a guide in their search for new avian species.

Rheindt and colleagues, a joint research team from the National University of Singapore (NUS) and the Indonesian Institute of Sciences (LIPI), targeted their search for new species around the islands of Taliabu and Peleng because of the deep sea waters lying between them and the larger island of Sulawesi to the southwest. Deep waters mean that land bridges can’t form between the islands and nearby bodies of land, even during glacial cycles. Because deep sea islands like Taliabu and Peleng have always been isolated, they are also more likely to harbor high levels of endemic species.

Taliabu and Peleng both lie in Indonesia’s Wallacea region, an archipelago named after British biologist and explorer Sir Alfred Wallace, who collected specimens of his own in the area. By examining the accounts of historic collectors like Wallace, Rheindt and team were able to determine that the islands they chose to focus on had not been extensively explored in the past. The Sula island group, which includes Taliabu, was only visited by eight collecting expeditions in the past, none of which ventured inland, instead sticking mostly to coastal areas. The Banggai group, which includes Peleng, was only visited by three historic collectors, who likewise did not explore the islands’ interiors.

Rheindt and team collected the ten new bird species and subspecies during six weeks of fieldwork, from November 2013 to January 2014, in the Sula and Banggai islands as well as in the Togian island group.

The researchers found three new species on Taliabu: the Taliabu Grasshopper-Warbler, the Taliabu Myzomela, and the Taliabu Leaf-Warbler. Three subspecies were also discovered on Taliabu: the Snowy-browed Flycatcher, the Taliabu Island Thrush, and the Sula Mountain Leaftoiler. Two new species, the Peleng Fantail and the Peleng Leaf-Warbler, were discovered on Peleng, as was a new subspecies, the Banggai Mountain Leaftoiler. The Togian Jungle-Flycatcher, another new subspecies, was found on the island of Togian.

“Studying the routes and operations of historic collecting expeditions and identifying gaps has been a fruitful approach to pinpoint focal areas in our case,” Rheindt said in a statement. “The description of this many bird species from such a geographically limited area is a rarity.”

While locals knew of some of the species already, it’s possible some of the birds had gone unnoticed because they sound more like insects. Rheindt told New Scientist that the Taliabu grasshopper warbler, for instance, sounds like a cricket, and that he heard its call long before he was able to lay eyes on one of the birds.

“When I heard it, I was aware that it was a type of grasshopper warbler, but it sounded very different from the ones that I knew,” says Rheindt. “I had a hunch that this would be a new species, but it took me a week or more to see them for the first time.”

Birds are one of the best-known groups of animals in the world, so much so that, over the past two decades, an average of just five or six new species have been discovered every year. Rheindt suggests that the methods employed by his team could be successfully applied to other regions and other types of wildlife: “Going forward, the use of earth-history and bathymetric information could also be applied to other terrestrial organisms and regions beyond the Indonesian Archipelago to identify promising islands that potentially harbour new taxa to be uncovered.”

The ten new birds may already be in need of conservation interventions. During their time on the islands, the researchers witnessed firsthand the extensive deforestation that has occurred on both Taliabu and Peleng. The islands’ primary lowland forest has been all but completely wiped out, the research team found, while most of the islands’ highland forests have been subjected to logging or forest fires.

“While most of the avifauna we described seems to tolerate some form of habitat degradation and is readily detected in secondary forest and edge, some species or subspecies are doubtless threatened by the immense levels of habitat loss on these islands,” Rheindt said. “As such, urgent, long-lasting conservation action is needed for some of the new forms to survive longer than a couple of decades beyond their date of description.”

CITATION

• Rheindt, F. E., Prawiradilaga, D. M., Ashari, H., Suparno, Gwee, C. Y., Lee, G. W., Wu, M. Y., & Ng, N. S. (2020). A lost world in Wallacea: Description of a montane archipelagic avifauna. Science, 367(6474), 167-170. doi:10.1126/science.aax2146

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