At the GELIFES PhD/Postdoc seminar on 16 April 2026, Delip K. Das, one of our PhD researchers at BirdEyes and the University of Groningen, presented research on the black-tailed godwit and how it is shaping our understanding of bird migration across Asia.
While the species is well studied in Europe—especially here, in the Netherlands, where it is the national bird—the Asian populations remain far less understood. Bangladesh lies at the intersection of two major migration systems, the Central Asian Flyway and the East Asian–Australasian Flyway, and hosts thousands of wintering godwits. Yet until recently, their origins and identities were largely unknown.
Working with a dedicated local field team, he captured 103 godwits from two key habitats: the coastal wetlands of Nijhum Dwip National Park and the freshwater ecosystem of Tanguar Haor. The birds were carefully measured, their DNA analysed to confirm identity, and fitted with satellite tags to track their movements.
His analyses confirmed the presence of three subspecies in Bangladesh—L. l. limosa, L. l. bohaii, and L. l. melanuroides—each linked to distinct breeding grounds across northern Asia, from Kazakhstan to eastern China. Satellite tracking showed that these birds regularly cross the Himalayas and the Tibetan Plateau, flying at altitudes above 6,000 meters in sub-zero temperatures. This is notable, as the Tibetan Plateau has long been seen as a major barrier that most migratory birds are thought to avoid. These findings offer rare insight into high-altitude flight.
Moreover, the research suggests that flight altitude is shaped more by topography than by temperature. Despite large temperature difference between spring and autumn migration, the birds did not adjust their flight heights. This challenges the current hypothesis that temperature alone determines high-altitude flight.
Among the most remarkable observations was the journey of an individual male godwit named Mubarak. In his first tracked year, Mubarak followed the westerly route typical for limosa from Bangladesh to breeding grounds in Kazakhstan. After returning, he moved to Thailand for the winter. The following spring, however, he took an unusual easterly route along the Chinese coast up to Bohai Bay— a typical route for a different subspecies (L. l. bohaii)—before eventually correcting direction toward Kazakhstan. This detour suggests that migration routes may be more flexible than previously thought.
Raised in the world’s largest delta, Delip refers to these birds as “delta sentinels,” connecting ecological knowledge across continents. His work not only fills key gaps but also highlights the Central Asian Flyway as a rich ecological theatre of bird migration.
Delip’s scientific journey is rooted in a personal reflection on home and belonging. Growing up away from his ancestral village- Tejkhali, Bangladesh, which he visited occasionally, he found a parallel with migratory birds—born in one place, traveling vast distances, and returning seasonally. This connection sparked a deeper curiosity about movement, place, and identity. It eventually led him to study black-tailed godwits (Limosa limosa) in Bangladesh
Delip’s research has been broadcasted in by Bengal’s WildTales .
