Radar studies revealed that millions of birds funnel through this narrow land bridge during migration. The aerial traffic jam makes it one of Asia's most important migratory bottlenecks.
The bottleneck effect
The Jaffna Peninsula, at the northern tip of Sri Lanka, is connected to the rest of the island by a narrow isthmus of land called Elephant Pass. This geography creates a natural chokepoint for migratory birds. It sits on the Central Asian Flyway, a major aerial route that extends from Siberia and northern Europe through Asia to its southernmost destinations. Millions of birds, from over 200 species, travel this path to overwinter in the warmer climate of Sri Lanka.
This narrow passage funnels an immense volume of avian traffic into a concentrated stream. The phenomenon is especially pronounced because the birds are crossing the Palk Strait from the Indian subcontinent, and Elephant Pass is a primary entry point to the island's wetlands and lagoons. The sheer density of birds passing through this corridor makes it a major migratory bottlenecks in Asia. Until recently, the full scale of this migration was difficult to quantify. The installation of specialized radar systems tracks this mass movement, even after dark when most songbirds travel.
Radar ornithology in action
Scientists use repurposed weather or surveillance radar to study the patterns of bird migration, a field known as radar ornithology. These systems emit electromagnetic waves and interpret the signals that bounce back, detecting the size, speed, and density of objects in the airspace. By filtering out weather-related signals, researchers can map bird movements. The radar can track individual flocks and provide data on flight altitude and speed, revealing how birds use wind currents to their advantage.
This technology is particularly effective for monitoring nocturnal migrations, which are nearly impossible to observe otherwise. Data from these systems helps conservationists understand which habitats are most important for birds to rest and feed. This information is used to assess the potential impact of infrastructure like wind turbines, which can pose a collision risk. Research groups like the Field Ornithology Group of Sri Lanka (FOGSL) use this data, along with traditional bird ringing and satellite tagging, to build a comprehensive understanding of migratory routes and protect important stopover sites. Among the many species observed are the Bar-tailed Godwit (Limosa lapponica), Curlew Sandpiper (Calidris ferruginea), Northern Pintail (Anas acuta), and Garganey (Spatula querquedula).
💡Fun Facts
The name "Elephant Pass" originates from the historical practice of guiding elephants across the shallow lagoon to the Jaffna Peninsula.
The area around Elephant Pass, including the Chundikulam Lagoon, was declared a bird sanctuary as early as 1938.
Radar ornithology can track the mass "exodus" of birds from their stopover habitats within minutes of sunset as they begin their nocturnal migratory flights.
Some birds that pass through Sri Lanka, like the Heuglin's Gull, travel as far as the Arctic regions of northern Russia, a journey of over 7,800 kilometers (4,800 miles).
The radar installation is a scientific research facility and is not open to the public. However, the surrounding areas offer excellent birdwatching opportunities.
Admission
Not applicable to the radar site. Nearby national parks may have entry fees.
Accessibility
The general terrain is flat coastal plains. Access to specific birding locations, like the lagoons and national parks, may require a vehicle suitable for unpaved roads.