A songbird species previously thought to occur across two Indonesian islands has turned out to be two distinct species, according to a recent study.
For more than 120 years, many scientists believed that Indonesia’s Babar Islands in eastern Banda Sea, and Tanimbar Islands, roughly 135 kilometers (84 miles) east of the Babar Islands, were both home to the cinnamon-tailed fantail (Rhipidura fuscorufa). But a team of researchers led by James A. Eaton of Birdtour Asia Limited and Alex J. Berryman of BirdLife International has confirmed that the songbird on Babar Islands is a distinct species, which they’ve named the cheerful fantail (Rhipidura laguceria).
To confirm these findings, the researchers analyzed 19 museum specimens of birds labeled cinnamon-tailed fantail, historically collected from both Tanimbar and Babar islands. They also recorded songs of the birds on both islands, then played the recorded calls back to the wild birds 132 separate times over several years.
The researchers found that physical differences between the populations on the two islands are subtle: The cheerful fantail possess slightly darker upperparts and less extensive cinnamon plumage below than the cinnamon-tailed fantail.
However, their songs vary considerably. The researchers said in the study that songs of the birds on Babar typically consist of “single whistles that rise in pitch towards the end.” By contrast, the Tanimbar birds combine very short and longer whistles, which gives their songs a “much more rhythmic cadence,” with pitch that typically goes up and down.
The song recording experiments also revealed that birds routinely responded to recordings of their own population, but ignored song recordings of birds from the other island.
Many birds rely on songs and calls to identify individuals of their species and find mates. So, birds from the two populations failing to recognize each other’s songs suggests they’re less likely to pair up and reproduce, the study authors said.
The cinnamon-tailed fantail is currently classified as least concern on the IUCN Red List. However, with the two populations on Babar and Tanimbar islands representing two different species, the known ranges for both species are significantly reduced, meeting the initial thresholds for listing as threatened, the authors said.
“However, both species are highly tolerant of habitat degradation (the only plausible threat), and are commonly found in edge habitats, clearings and glades, as well as scrub with taller mango trees,” the authors said, adding that both fantails seem to favor “heavily modified habitats” while generally avoiding “closed-canopy forests.”
Indonesia’s Babar Islands remained largely unvisited by ornithologists for a century until 2009.
Banner image: The Cheerful Fantail (Rhipidura laguceria). Image courtesy of James A. Eaton via iNaturalist (CC0 1.0).
