Rote Leaf Warbler: New Bird Species Discovered in Indonesia

A striking new species of leaf warbler has been discovered in the forests of the Indonesian island of Rote by an international team of researchers. The discovery is outlined in the journal Scientific Reports.

The Rote leaf warbler (Phylloscopus rotiensis) has a characteristic long bill. Image credit: Philippe Verbelen.

Named the Rote leaf warbler (Phylloscopus rotiensis), the new bird species is endemic to Rote Island, the province of East Nusa Tenggara, Indonesia, where it inhabits intact primary deciduous forest as well as secondary forest.

“Rote Island is a dry monsoon island with an area of 1,200 km². It is around 7.5 miles (12 km) off the coast of Timor, and about 310 miles (500 km) northwest of Australia,” the ornithologists said.

“The island is also the site where a bird species new to science, the Rote myzomela (Myzomela irianawidodoae), was recently discovered.”

The presence of a leaf-warbler of unknown identity on Rote was first noted in December 2004 by Charles Darwin University’s Dr. Colin Trainor.

In July 2009, Belgian birdwatchers Philippe Verbelen and Veerle Dossche made detailed observations and obtained a series of photographs of the bird.

“Alarm bells went off when we realized how strikingly different the bill shape and the coloration of the Rote bird were compared to all other leaf-warblers,” Verbelen explained.

The Rote leaf warbler (Phylloscopus rotiensis). Image credit: Philippe Verbelen.

The Rote leaf warbler is a small songbird, measuring 4 inches (10.3 cm) in total length and weighing 7.5 g. It has a wingspan of 6.1 inches (15.5 cm) and a tail that is about 1.5 inches (3.8 cm) long.

“The new species is part of a large group of Asian warblers but is unique among them due to its unusually long bill (about 0.6 inches, or 1.6 cm),” said team member Dr. Nathaniel Ng, a researcher in the Department of Biological Sciences at the National University of Singapore (NUS).

“This odd bill shape is likely an adaptation to Rote’s dry landscapes, given that most other Asian leaf-warblers live in humid forest.”

The scientific description of the Rote leaf warbler was partly aided by an analysis of genome-wide data collected through next-generation sequencing.

“This may well be the first time — to the best of our knowledge — that a new bird species has been described partly on the basis of genome-wide DNA data,” said team member Elize Ng, also from the NUS Department of Biological Sciences.

“This work would not have been possible without the partnership with the Indonesian Institute of Science, and in particular, with Dr. Dewi Prawiradilaga,” said team leader Dr. Frank Rheindt, also from the NUS Department of Biological Sciences.

Due to Rote Island’s long history of intensive agricultural use, there is little forest habitat on the island with the exception of two forest areas.

“We propose that the Rote leaf warbler be given an IUCN (International Union for Conservation of Nature) categorization of ‘Vulnerable’ under criteria B1 and B2 of the 2001 IUCN red list criteria,” the researchers said.

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Nathaniel S.R. Ng et al. 2018. A striking new species of leaf warbler from the Lesser Sundas as uncovered through morphology and genomics. Scientific Reports 8, article number: 15646; doi: 10.1038/s41598-018-34101-7