Society

Eighteen-year-old girl from Chennai presents first documented record of an Eastern Yellow Wagtail sighting in Tamil Nadu

The Eastern Yellow Wagtail recorded and photographed at IIT-M on October 26, 2020. Photo: Mahathi Narayanaswamy  

Birders can relate to the Aesop’s fable where a hare is in a flap, convinced his upstanding ears would be mistaken for horns.

The lord of all he surveys, the lion has given all the animals that sport horns the marching orders, banishing them out of the jungle.

Why? While sinking his unusually-sharp molars into a goat and making a meal of it, the lion had found the bovid’s horns spoiling the good-dining experience. Hence, the draconian measure.

Now, seeing the shadow of his own ears, the hare believes the lion would certainly take them for horns, and so leaves the jungle without being ordered to.

Just the same way, birders can find physical features of birds playing tricks on their eyes where two closely-related, incredibly similar-looking bird species and subspecies are being identified in the field.

Wrapping one’s head around the various sub-species of the Western Yellow Wagtail —which occurs in large numbers in the Indian sub-continent during winter — can tantamount to solving the Goldbach Conjecture.

Now, going by a recent finding that has been elaborately documented in eBird, Indian birders should be looking for the Eastern Yellow Wagtail as well. Once bracketed along with the sub-species of the Western, the Eastern Yellow Wagtail has come to be recognised as a separate species, with a clutch of sub-species of its own.

In regions where Eastern Yellow Wagtail and the Western Yellow Wagtail occur together, especially in their winter finery, birders may be required to go beyond the visual and tune in to a bird’s call for a clue into its essence.

The call matters

Eighteen-year-old Mahathi Narayanaswamy, a birder and resident of the IIT-M campus in Guindy, recorded a Yellow Wagtail’s call, and largely by how it sounded, eBird has approved the bird as an Eastern Yellow Wagtail.

Mahathi Narayanaswamy

Mahathi Narayanaswamy  

“Mahathi’s is the first known record of an Eastern Yellow Wagtail sighting in Chennai and the whole of Tamil Nadu. Mahathi saw the bird on October 26, 2020, at IIT-M,” says eBird reviewer Vikas Madhav Nagarajan, adding that she recorded the call, took a video and got a picture of the bird.

Mahathi points out that eBird reviewer Ashwin Viswanathan from Bengaluru had been the driving force, motivating her to ‘listen’ as well as ‘look’ for the Eastern Yellow Wagtail during her winter field visits.

At a surface level, features distinguishing the Eastern Yellow Wagtail from the Western are: paler grey on the forehead and nape, and darker lores, and a more prominent supercilium.

There is apparently a problem here.

“Eastern and Western Yellow Wagtails are challenging to differentiate based on appearance, especially in their wintering range in India. Recording of their calls is the best way to tell them apart. Their calls are not drastically different for an untrained ear or one that is not familiar with the call but however it is the best means of differentiating,” says Mahathi.

“When it comes to our side — Tamil Nadu — it (Eastern Yellow Wagtail) comes in a weird mould. It is very difficult to separate from the Western Yellow Wagtail, which we normally get,” adds Vikas.

Sequence of events

Here is the sequence of events that led to the record of the Eastern Yellow Wagtail on Chennai soil.

“In February 2020, in one of the bird ID groups, someone wanted to know the differences between a Citrine Wagtail from a Yellow Wagtail. I posted a photo of a ‘Yellow Wagtail’ I had taken four years ago at IIT-M to explain the differences. Seeing the photo, Ashwin Viswanathan told me this bird resembled the Eastern Yellow Wagtail. The lores were darker. However, there could not be any absolute certainty about its identity without listening to its call. And there was no recording of the call to go with it,” narrates Mahathi.

At that time, Mahathi was in school and in Class XII and could not devote much time to birding. So, that birding season passed.

On October 26, 2020, again at IIT-M, she saw what turned out to be an Eastern Yellow Wagtail, with Ashwin confirming it after studying the documentation, which included the bird’s call.

An Eastern Yellow Wagtail shot in October 2016 at IIT-Madras. Photo: Mahathi Narayanswamy

An Eastern Yellow Wagtail shot in October 2016 at IIT-Madras. Photo: Mahathi Narayanswamy  

Sound judgement
  • Mahathi Narayanaswamy is joining the Azim Premji University in Bengaluru to study physics. The eighteen-year-old is viewed as a whiz kid in birding circles. So, the logical question: “Would ornithology be the next stop?”
  • Mahathi answers it this way: “I want to use physics to explain bird behaviour.”
  • Mahathi has already got her talons into formal birding techniques, having attended the Cornell Young Birders programme at Ithaca in New York, in 2018; and a sound recording workshop at National Centre for Biological Sciences (which comes under the Tata Institute of Fundamental Research) in 2019. Mahathi says the workshop has “helped me especially with editing and processing bird recordings.”
  • Mahathi believes that while presenting a record of a bird sighting for any online database of avian observations — such as eBird — having a recording of the bird's call adds considerable value to the exercise.
  • “One can record a bird call without fancy or expensive equipment,” says Mahathi.
  • An app in the mobile is just what the doctor ordered.
  • “For android users, Recforge is a good app. And for iphones urser, it is Rode,” elaborates the young birder. “And for bird calls we would always recommend recording in .wav.”
  • Why .wav?
  • “Mp3 and m4a produce highly compressed recordings and are generally low quality sound files. .wav also gives you a bit more control with your recordings,” says Mahathi, and suggests https://support.ebird.org/en/support/solutions/articles/48001064305-smartphone-recording-tips for anyone looking for guidelines for recording.
  • Mahathi knows that people are generally reluctant to make recordings of bird calls, but that does not make they any less critical in not just bird species identification, but also classification.
  • “There are species that have been split after bird calls have been analysed and genetic analysis have been done."
  • Bird calls can sometimes lead one up the garden path — here, we are dealing with not just birds that can mimic other birds’ calls.
  • “There are species whose calls are very similar, but at the end of the day birds can recognise differences. Sometimes there are harmonica that make two calls different from each other, and which are not audible to the human ear. So in such cases, finding the bird is the best thing to do.”
    • “Ashwin pointed out that the Eastern Yellow Wagtail has a raspier and shorter call,” says Mahathi.

      “The Eastern Yellow Wagtail has a high-pitched, harsh and shorter call. In contrast, the Western Yellow Wagtail has a sweeter and longer call,” says Vikas. “On the sonogram, a Western’s call will ascend and drop gradually. The Eastern’s call will have markings suggesting abruptness.”

      This month, Vikas recorded the call of a Yellow Wagtail he saw at Karapakkam, and sent it to Ashwin, who has confirmed it as an Eastern Yellow Wagtail. Vikas’ sighting is in queue for approval at eBird.

      Mahathi says that now it is known that the Eastern Yellow Wagtail has all along been missed in the field.

      Not surprising, when you consider that even identification of the Western Yellow Wagtail is not done granularly, as the birds are not named according to the sub-species they belong to.

      “Even eBird does not have filters to name the various sub-species,” says Mahathi. “There is no clarity about the subspecies occurring in India.”

      Mahathi and Vikas have undertaken a project to record calls of Yellow Wagtails (at IIT-M), with the objective of assessing the Eastern’s population.

      Says Mahathi, “We have only got Westerns so far. However, we have one hour more of recording to sift through, so there is no telling what is in there.”

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      Printable version | Jan 18, 2021 3:52:55 AM | https://www.thehindu.com/society/eighteen-year-old-girl-from-iit-m-presents-first-documented-sighting-of-an-eastern-yellow-wagtail-in-tamil-nadu/article33192440.ece

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