In a groundbreaking study, scientists have mapped the intricate seasonal journeys of common cranes wintering in Gujarat, revealing they take massive detours to avoid the formidable Hindu Kush mountains. This research provides the first detailed look at the migratory bottlenecks and adaptive strategies of the species along the Central Asian Flyway (CAF).
The Desert Corridor: A Strategic Detour
Researchers from the Wildlife Institute of India (WII) fitted five adult common cranes with solar-powered GPS-GSM transmitters during the winters of 2019-20 and 2021-22. The birds were tagged at the Nal Sarovar and Thol Lake bird sanctuaries in Gujarat. Over three years, these birds completed nine full migration cycles between their Indian wintering grounds and breeding sites in southwestern Siberia and northern Kazakhstan.
The data painted a clear picture: the cranes' routes were far from direct. Their spring journeys were almost 37% longer than the shortest possible path, while autumn routes exceeded the shortest distance by more than 23%. Instead of attempting a direct flight over the towering Hindu Kush range, the birds consistently diverted westwards.
This detour took them through Pakistan, Afghanistan, Iran, Turkmenistan, and Uzbekistan before they turned northeast towards the steppes. Scientists propose naming this circuitous path the "desert corridor" of the Central Asian Flyway.
Why the Long Way Around?
The detour, though longer in distance, is a calculated energy-saving strategy. The expansive desert regions along this route—including the Karakum in Turkmenistan, Dasht-e-Margo in Afghanistan, and Kharan in Pakistan—generate strong thermal updrafts. These rising columns of warm air allow the large birds to soar effortlessly, conserving crucial energy for their long voyage.
Furthermore, this desert corridor provides scattered but reliable stopover habitats. The study found that cranes have the highest probability of using bare ground and agricultural fields during their stops. These open landscapes offer essential foraging opportunities and clear visibility to spot potential predators.
The research also uncovered clear seasonal differences in migration behavior. The spring migration northwards is slower, longer, and involves more frequent stops, likely to build up energy reserves before the breeding season. In contrast, the autumn return to India is comparatively faster and more direct, with fewer stopovers.
Bottlenecks and Emerging Threats
A critical finding of the study is the identification of major migratory bottlenecks where all tracked routes converged into narrow corridors. These chokepoints are located in southern Turkmenistan near the Tejen river, the northwestern Dasht-e-Margo desert in Afghanistan, and Pakistan's Kharan desert.
The landscape naturally funnels thousands of cranes through these specific regions, making the population exceptionally vulnerable there. Threats like habitat loss, hunting, and illegal trade—still widespread in parts of Afghanistan and Pakistan—pose a significant risk. "When most of the population passes through a single narrow corridor, even local disturbances can have serious consequences," warn the study authors.
An additional rising concern is disease risk. Several identified stopover sites host high densities of various migratory birds, creating hotspots for potential pathogen spread. This is especially alarming following recent outbreaks of highly pathogenic avian influenza, which have caused mass mortality in common crane populations elsewhere.
A Call for Cross-Border Conservation
Given that Gujarat hosts a significant portion of the regional wintering population of common cranes, the tracked birds are believed to represent a substantial share of the population using this flyway. The findings underscore an urgent need for coordinated, international conservation efforts.
Protection measures must span multiple countries, including Pakistan, Afghanistan, Turkmenistan, Uzbekistan, and Kazakhstan. The authors conclude that the common crane acts as a strong indicator of the overall health of the Central Asian Flyway. Conserving its critical desert, floodplain, and steppe stopover habitats would benefit a multitude of other migratory species that share this aerial highway.
The study was conducted by WII PhD scholars Harindra Baraiya and Gaurav Sirola, along with senior scientist R Suresh Kumar and former scientist Anju Baroth. The paper was published in the journal Animal Biotelemetry. The project received financial support from the Powergrid Corporation of India Limited and assistance from the Gujarat state forest department.
