Rote myzomela: Honeyeater’s new tune
How bioacoustics is helping ornithologists to discover new species
So far this is the best piece of news in natural history this year. A new species of bird has been found and a young Indian scientist is credited with having played a pivotal role in the discovery.
The Rote myzomela is an endemic species of honeyeater from the tiny Indonesian island of Rote, which falls in the biogeographical region of Wallacea in the Indo-Australian archipelago. On the map, Rote is just a speck of land south-west of Timor island.
“We have named the bird Myzomela irianawidodoae after the Indonesian first lady Iriana Joko Widodo to promote the conservation of the bird and its habitat, which is already threatened by deforestation in the remote island," says Pratibha Baveja, co-author of the research paper A Colourful New Species Of Myzomela Honeyeater From Rote Island In Eastern Indonesia.
Baveja, a PhD student at the avian evolution laboratory, National University of Singapore, worked on the bioacoustics analysis, morphological diagnosis and manuscript preparation.
For 28 years, ornithologists and birdwatchers have mistaken the Rote myzomela for the Sumba myzomela because of the near-exact plumage—a bright scarlet head, with the colour extending to the breast, a black body with a scarlet rump. The other three closely related honeyeaters found in the Wallacea region are the Red-headed myzomela (which has a similar head pattern), Timor myzomela and Banda myzomela.
In 1990, when the Australian ornithologist Ron Johnstone first spotted the honeyeater on Rote Island, he couldn’t get a photograph or a sound recording. Johnstone assumed the species to be the Sumba myzomela. There had been no further studies on the Rote Island honeyeater and books classified the bird as the Sumba myzomela (Myzomela dammermani). It was only in 2009, when two Belgian birders, Philippe Verbelen and Veerle Dossche, recorded the calls that doubt crept in.
To the uninitiated, the Rote myzomela’s vocalizations are pleasant, chirping that one would enjoy waking up to, while the Sumba myzomela’s sounds are more complex, like a code, with many more variations.
The recordings of the Belgian birders kick-started a series of ornithological expeditions to investigate and record the honeyeater’s calls. Finally, in 2015, four specimens were collected for morphological and genetic analysis by a method known as mist netting, after due permissions.
“There have been few bioacoustics studies of honeyeaters. When we conducted the vocalization analyses of the Rote myzomela and Sumba myzomela, we found each taxa had its unique call types. The vocalizations of the Rote myzomela are monotonous, uniform and repetitive, with less vocal variations, like a series of chirps. In contrast, the vocalizations of the Sumba myzomela are complex and have an undulating warble. These distinctions were just qualitative. In order to have stronger evidence, bioacoustics analysis was necessary. In bioacoustics, you can basically look at the sound through sonograms, which are visual depictions of vocalization," says Baveja.
The research demonstrates the differences between the vocalizations of these two similar-looking honeyeaters and the importance of bioacoustics data in species diagnosis when morphological distinctions are limited. “Vocalizations can be a more reliable taxonomic indicator in some birds than morphological traits," says Baveja.
In 2016, another Indian ornithologist, Shashank Dalvi, was part of the international research team that discovered the Himalayan Forest Thrush through bioacoustics. Till then, the Plain-backed Thrush was considered a single species in the North-East and in neighbouring China. Thanks to bioacoustics and genetic research, the Plain-backed Thrush underwent a three-way split—Himalayan Forest Thrush, Alpine Thrush and the Sichuan Thrush (in China).
In birds, songs are used to attract mates and in courtship, while calls could be contact calls or alarm calls. “In the case of myzomela, the wide repertoire of vocalizations makes it difficult to distinguish between these two. So, we have compared call types that were shared between the two species," adds Baveja.
Honeyeaters are known to respond strongly to the playback of intraspecific songs, looking upon this as a sign of aggression among competing males. In the field, the Belgian ornithologists tested this. The Rote myzomela did not respond to the playback of vocalizations of the Sumba myzomela, and vice versa. However, when vocalizations of myzomela individuals from the same island were played, it triggered an aggressive territorial response in the birds. This helped the researchers establish that the bird population from the two islands consists of distinct species.
New species discovery in birds is rare—birds are one of the most well-researched taxa in science—but scientists are hopeful that tropical islands such as Rote can still spring a surprise or two if rapid deforestation is stopped and development is done in a sustainable manner.
Out In The Wild is a column on the good, bad and ugly of nature conservation.
The writer tweets at @protectwildlife