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News overview
11 September 2023

On the tail of elusive godwit subspecies

Delip Das, PhD student from Bangladesh, is working with renowned RUG ornithologist Theunis Piersma. His pioneering fieldwork is shedding light on the migration routes of godwit populations in Bangladesh, which have never been studied before. “My vision is to use godwits as a monitoring tool to help maintain a healthy delta. This is very relevant to the Netherlands as well.”

Text: Nienke Beintema, photos @Shariful Islam

Godwits, with their majestically long legs and bills, have been ambassadors of Dutch ‘agricultural nature management’ for some decades now. Declining steeply in recent years, they have been studied extensively both in The Netherlands and in their wintering areas along the Mauritanian coast, by researchers such as RUG professor Theunis Piersma. Few people know, however, that the same species of godwit is also found in other parts of Eurasia. Populations that breed in Central Europe, Siberia and China, for instance, spend their winters in Bangladesh. But no-one knows exactly how these populations migrate, how many different ones they are, and which challenges they meet throughout their annual range.

Delip Das, biologist from Bangladesh, came to Groningen to unravel these mysteries. “This knowledge is needed to effectively protect the godwits of this part of the world”, he says. “And it may also contribute to our understanding of European godwits.”

Tell us about these godwits in Bangladesh.

“Bangladesh is ecologically very interesting: it lies in between the Indian and the Thai-Malaysian peninsulas. The country is basically one big wetland, being the delta of several large rivers that come down from the Himalayans. Two groups of godwits spend their winters here: one in wetlands in the north, and one along the tidal coastal zones of the south. We know that different subspecies are mingling there, but we don’t know how many, or where they come from. There may be as many as 10,000 to 20,000 godwits, but there may be additional groups in unknown places. These ecosystems in the north and the south are very different. I was wondering: why do they chose such different locations? In my mind, the south would be a far superior wintering location in terms of food availability. But this has never been studied before. It is one big black box.”

Why is it important that these questions are answered?

“If we want to protect migratory birds, we need to protect all relevant sites along their flyways. Understanding how and why they choose their wintering sites is part of that. There may be competition for food, for instance, or anthropogenic pressures like bird hunting, rice cultivation, fishing and agriculture. I am trying to understand the pressures and the ecological constraints these birds face, so we can hopefully protect them more effectively in the future.”

What’s your fieldwork like?

“It is adventurous and complicated. Remote, dangerous, and also really hard work. But I love such adventures. Imagine being on the mudflat at midnight, it’s new moon and pitch dark. It’s January: cold, windy and foggy. You have nets out to catch godwits, in the hopes of fitting them with GPS tags. You’re up to your chest in the water, and the tide is coming in. Every half hour you check all the nets and in between, you huddle together with your assistants to stay warm. And you catch nothing, haha!”

Really? Then what do you do?

“One night, this scenario was happening again – no luck. Suddenly I heard a few thousand godwits going on the wing. A very cool noise, like a jet plane taking off. I thought: that’s it for tonight, we won’t see them again. But then it turned out they had landed right next to our tent. I shone my torch and there they were: 3,000 godwits in a tiny wetland. You could hear all their calls – a magical sound. So the following night we set our nets right there, wading through deep sticky mud full of leeches. I got stuck: someone had to rescue me. It was a hell of an adventure, but in the end we caught thirteen godwits that are now carrying GPS tags. An amazing result.”

Is it the adventure that’s driving you…? Or scientific curiosity?

“It is actually my love for birds – and scientific curiosity for solving puzzles. In the process, I enjoy the adventure my expeditions bring along. You cannot sustain this if you don’t like the adventure. This spring I will be doing this fieldwork again, hopefully to fit forty more GPS tags.”

How did you become interested in biology?

“I already liked the subject in high school, so I decided to study biology. During my Bachelor’s research, I fell in love with an amazing bird species, the Indian skimmer. Such an intriguing and elegant bird: the way it glides over a water surface, skimming the water with its lower bill. So I also fell in love with mud and water.” He laughs. “Not with the cold water you have here, though. Anyway, for many years, also during my Masters, I studied this bird species, which is endangered, partly due to unsustainable fishing.”

Then why godwits?

“As my research progressed, I realized I didn’t have enough skills or expertise to really make a difference, nor did I have the professional network. In 2018 I attempted to attend a conference of the International Wader Study Group, an international expert group. This meeting was in Portugal. However, my visa application was rejected. I was heartbroken, especially since it was the second time a visa fell through for me. It was shattering. Colleagues and friends kept me motivated and encouraged me not to give up. Then, I read a paper by Theunis Piersma and saw a clip of his research set-up with red knots at NIOZ at Texel. I though to myself: this is what I want! These crazy people in The Netherlands – they’re doing it all, and they know all about marshes and mudflats. Then, by a stroke of luck, the next Wader Study Group meeting was in Workum in The Netherlands and I finally got to go. It was amazing. This was my home, these were my people.”

Did Theunis have a job for you?

“Not immediately, no. He of course had his funding constraints, and he already had enough PhD students. For a few years I kept writing to him. In fact I was stalking him.” Das laughs heartily. “Theunis was very interested, though, so he asked me to put my ideas in writing, which I did. In the end, he did find some money – and I got additional funding from the Dutch and French embassies in Dhaka for my fieldwork, which is relatively expensive because it is so remote and complex. In any case, I finally got to come to Groningen. I was so happy.”

And, how is it going so far?

“Worldwide, there are four subspecies of godwit, including newly discovered bohaii subspecies. Bohaii godwits were discovered from China in 2021 by Bing-run Zhu, another PhD student of Theunis. My genetic work identified three subspecies of godwits in Bangladesh, which is new information. It seems Bangladesh is a global hub for most of the godwits populations in the world. We found that the inland, northern population also uses southern coastal mudflats when the northern habitat is unavailable to them.”

What else did you discover?

“From the GPS tags, we now know that godwits fly across the Himalayans even at higher altitudes than the famously high-flying bar-headed goose. Previously, it was thought that godwits avoided the Himalayans. Incredible how they navigate such a rugged landscape, with these altitudes and icy storms. In addition, like in the Netherlands, the godwits in Bangladesh are sentinels for soil biodiversity, and thereby for ecosystem quality. My vision is to use godwits as a monitoring tool to help maintain a healthy delta.”

Are you an optimist in that regard?

“I’m quite confident that my research will contribute to making that vision a reality. It is definitely going to produce more knowledge – and this will benefit people as well. Bangladesh will be an ideal place to come up with new, innovative approaches to conservation in one of the most densely populated areas in the world. You can’t just say: people can’t use those areas anymore. You need to find a way to shift towards land use that allows people and wildlife to coexist – which is very relevant in your country as well. The parallels are striking.

I hope that my research will bring new perspectives – ones that are important to the entire flyways of this species. It is an unexplored world. It is about time that we change that.”

Delip Das (1986) studied Biology at Jahangirnagar University in Bangladesh. He then completed a Masters in Bioinformatics at the University of Mumbai, India. For the past 10 years, he has been teaching at Jagannath University in Dhaka, Bangladesh – since 2016 as an assistant professor. In April 2021, Das started a PhD project at the RUG.

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