The ancient Sanskrit epic Ramayana has it that Hanuman was a mighty ape god who marshaled an army to build a bridge linking northern Sri Lanka’s Mannar region with South India’s Rameswaram. Several hundred years later, a small bird species new to science is named as the Hanuman plover, as it lives and was found in the vicinity of the mythical bridge and it’s the first specimen to help distinguish the plover from other shorebirds.

“We selected Hanuman plover as the bird’s common name to celebrate the mythology linked to the native land of this plover,” says Sampath Seneviratne, a professor in zoology attached to the University of Colombo who conceptualized the study. The bird is scientifically categorized as Charadrius seebohmi honoring Henry Seebohm, the British ornithologist who, as far back as 1887, first suggested the Sri Lankan breeding population could be a possible distinct species, Seneviratne told Mongabay.

The Hanuman plover was initially thought to be a subspecies of the Kentish plover (Charadrius alexandrinus), hence scientifically categorized as Charadrius alexandrinus seebohmi, in 1848. The Kentish plover is a common shorebird found in Eurasia and North Africa, and those that breed north of 40° latitude are the winter migrants. Kentish plovers migrate to Sri Lanka in large numbers and fly back to breeding grounds after the migratory season — except one population that chooses to remain in the Indian Ocean island throughout the year.

Some migratory birds, known as the “loiterers,” do not go back for a season or two, but this Sri Lankan and South Indian population is quite different, as the birds also breed. Whenever he spotted a Kentish plover outside the migratory season, Seneviratne was driven by curiosity about where they come from and why they appear to breed on the island.

A distinct population

Seneviratne left Sri Lanka in 2008 for his Ph.D. in evolutionary ecology, but his obsession to unravel this mystery was never quenched. During a 2009 holiday, Seneviratne specifically rented a cabin in Mirijjawila, a remote southern village in Sri Lanka, to observe a Kentish plover nest. He spent two full days observing the hatchling, ignoring the scorching sun, to record its calls.

Global reviews on plovers continue to highlight the possibility that some plover subspecies could be new and distinct species. Meanwhile, the genetic studies helped elevate the Chinese subspecies as being distinct, and in 2019, it was named as a white-faced plover (C. dealbatus) by a team led by Yang Liu of Sun Yat-Sen University in China.

After this, Seneviratne’s thirst for a study of the Sri Lankan breeding Kentish plover subspecies further increased. During one of the meetings, Seneviratne showed Yang a video of a nesting plover in northern Mannar, carefully filmed by one of his students. Identifying the potential, Yang agreed to collaborate on the study of the Sri Lankan and South Indian species.

The next challenge was to find a team to conduct the field study. Luckily, Seneviratne had the perfect match — the student who filmed the ground nesting plover, Jude Janitha Niroshan. This plover lives in the arid zone, and a field study meant extensive hours under the scorching sun and dirty mud plains, yet Niroshan’s interest in the Mannar study overcame all of that. The team collected data from 937 birds from 29 field locations from Sri Lanka as well as the Chinese coast.

Genetic comparisons

The fieldwork is just one aspect of the study. The team had to do extensive laboratory work, too, as they wanted to study the genetics comparing specimen of similar species. The original type specimen of the C.a.seebohmi was part of Walter Rothschild’s private collection in the United Kingdom and in the 1930s, was sold to American Museum of Natural History. In 2020, the team got lucky. The museum was under a COVID- 19 lockdown and was open only for official work for a limited time.

However, the team’s effort didn’t go to waste, as results of the genetic analysis threw up sufficient evidence to support that the Sri Lankan and the Indian breeding plover population was, in fact, a distinct species. So, a new generation of scientists are finally unraveling that a bird thought to be a distinct species over a century ago is, indeed, distinct.

The analysis also showed the breeding group is genetically and phenotypically distinct from the migratory Kentish plovers and the Chinese white-faced plover. The genetic analysis revealed the Hanuman plover diverged some 1.19 million years ago, Niroshan told Mongabay.

Despite their highly mobile nature, for the migrants, islands can be refuge from predators or places the birds have recently colonized. It is suggested that the sea level rise across Adam’s Bridge may have gradually created a suitable coastal nesting habitat. Over time, the individuals that bred in Sri Lanka gradually evolved to be different from those of the mainland, said Alex Bond, principal curator of birds at the Natural History Museum in Tring, in the United Kingdom, and a co-author of the research paper.

Safeguarding endemism

In a time of global biodiversity collapse, understanding what we must protect is an important building block in conservation, and this is especially true for islands, where high rates of endemism can mean more pressure on limited funding, said Bond. In this case, the Sri Lankan population might have been passed over under the assumption that it was the same Kentish plover that existed in abundance elsewhere. But by showing that the Hanuman plover is unique, the research illustrated that conservation efforts can be more focused, Bond said.

Sri Lanka is home to about 500 bird species with 220 breeding residents and 250 migrants. Among the breeding residents, 34 bird species are endemic to the country, but a further 80 species are endemic subspecies that are found only in Sri Lanka.

A subspecies is one of two or more populations of a species living in different areas of the species’ range and having different physical characteristics from one another such as body size, shade of the plumage, beak, tail and so on.

A common criterion for recognizing two distinct populations as subspecies rather than full species is their ability to interbreed. But in the wild, subspecies usually do not interbreed due to geographic isolation or sexual differences, so there is potential for them to in fact become distinct species. The advent of genetic research techniques helps unravel such hidden potential, and more studies like the one on the Hanuman plover may further elevate endemism among Sri Lanka’s avifauna, Seneviratne told Mongabay.

Banner image: A Hanuman plover, previously identified as a subspecies of the Kentish plover, despite their breeding habit continuing to puzzle ornithologists for centuries. Image courtesy of Thushara Siriwardana.

Photos: Sri Lanka’s Kalametiya lagoon draws tourists to see native and migrant birds

Citations:

Niroshan, J. J., Liu, Y., Martinez, J., Que, P., Wei, C., Weerakkody, S., Panagoda, G., Weerasena, J., Amarasinghe, T. A. A., Szekely, T., Bond, A. L., Seneviratne S.S. (2023). Systematic revision of the ‘diminutive’ Kentish Plover (Charadriidae: Charadrius) with the resurrection of Charadrius seebohmi based on phenotypic and genetic analyses. Ibis (2023). DOI: 10.1111/ibi.13220.

Wang, X., Que, P., Heckel, G., Hu, J., Zhang, X., Chiang, C., … Liu, Y. (2019). Genetic, phenotypic and ecological differentiation suggests incipient speciation in two charadrius plovers along the Chinese coast. BMC Evolutionary Biology, 19(1). doi:10.1186/s12862-019-1449-5