In the late 1980s, naturalist V Santharam noticed something puzzling. The familiar pond heron, also known locally as the paddy bird (Ardeola grayii), which usually occupies ponds and marshes, would disappear from mid-June until the end of September. “This used to happen around the Adyar estuary, where I spent every weekend observing birds,” he recalls. “I came across the same emptiness in several wetlands around Chennai whenever I visited them during those months.”
More than thirty years later, birders along the East coast are reporting the same pattern.
Santharam found that the birds would reveal themselves around the middle of October . On one such evening, he observed flocks of pond herons and cattle egrets flying southward with quiet determination. “This altered my understanding of what we assumed to be non-migratory birds,” he says. “I began maintaining notes on this pattern.” When he shifted to Puducherry, to pursue his doctoral studies, he saw the same pattern unfold. In October and November, he recorded repeated night flights of pond herons and cattle egrets, always oriented in roughly the same direction. Pond herons travelled in modest groups of seven or eight, seemingly without a fixed arrangement. Cattle egrets, however, formed larger groups, sometimes 20 to even a hundred birds moving with far greater coordination. “Their collective movement suggested a planned seasonal relocation,” he says.
IN 2022, Visakhapatnam birding enthusiasts and Nature educators Vivek Rathod, V Bhagyasree and Yagnapathy Adari independently observed the same night movements. What began as informal curiosity developed into a structured citizen-science effort. Vivek and several birders have now spent three consecutive years documenting the flights.
“The onset of winter brings numerous migrant species to our region, and we have also been observing the nightly movements of cattle egrets and pond herons,” says Vivek. “Our collective notes suggest a directional movement from the northeast towards the southwest.” According to him, the flights usually begin shortly after dusk, around 6pm, and continue well into the night.
Cattle egrets resting on top of a tree during a windy morning in Dindigul, Tamil Nadu.
| Photo Credit:
KARTHIKEYAN G
A flock of cattle egrets near Mangamaripeta beach in Visakhapatnam.
| Photo Credit:
KR Deepak
Santharam published his early observations in the Newsletter for Birdwatchers, a bi-monthly publication established by Zafar Futehally, noted naturalist and former secretary, Bombay Natural History Society. Although his note drew interest, he received very few corroborating reports from other regions. The absence of parallel documentation made the behaviour even more enigmatic, particularly because both species are widely seen across the country and are usually considered too common to attract extended study.
A flock of pond herons flying under the floodlights at the ACA-VDCA International Cricket Stadium in Visakhapatnam.
| Photo Credit:
KR Deepak
Now, local groups, including Wildlife Conservation Through Research & Education (WCTRE), have begun encouraging residents across Visakhapatnam to track of these movements, note flock sizes and record the locations where sightings occur. Among the areas that have seen repeated activity are Visalakshinagar, Shivajipalem, Pithapuram, Maddilapalem, Rama Talkies junction, the Beach Road stretch, Dabagardens, Zilla Parishad, the old quarters of One Town and the slopes around Dolphin Hills. “The birds pause in green patches within the city and resume their movement later in the night,” Vivek explains.
A pond heron takes off from the water lilies filled Kolarampathi tank in Coimbatore.
| Photo Credit:
PERIASAMY M
Why these species undertake such seasonal travel remains an open question. Santharam believes the movement may be associated with the availability of water. Much of Tamil Nadu and coastal Andhra Pradesh receives limited rainfall from the Southwest monsoon, leaving many wetlands dry by mid-year. “When water levels decline, food availability also changes,” he says. “The birds may be compelled to travel to places that can support them during that period.”
Vivek offers a parallel explanation rooted in agricultural cycles — pond herons and egrets appear in large numbers during the paddy-growing months, when fields support abundant prey, and decline after harvest. Vivek offers a parallel explanation rooted in agricultural cycles. The birds appear in large numbers during the paddy-growing months when fields support abundant prey. Once those fields are harvested and the landscape becomes unsuitable for foraging, their numbers diminish. They re-emerge during the post-monsoon months, take flight and move steadily southwards.
A cattle egret arrives to feed on insects in Morigaon district of Assam.
| Photo Credit:
RITU RAJ KONWAR
Santharam notes that adaptability may differ between the two species, with pond herons foraging more flexibly while egrets vanish almost completely in dry months
According to his long-term observations, the southward movement may be taking them towards the Rameswaram coast and possibly onwards to Sri Lanka. Whether they travel further or settle temporarily along intermediate wetlands has not yet been established. “We require more systematic study before we can draw definite conclusions,” he says.
A solitary observation that began in the 1980s is now beginning to form a larger pattern that spans regions, seasons and decades. As citizen groups and researchers continue to gather information, each year’s night skies add to this puzzle of two otherwise familiar birds, whose journeys are only now being documented closely.
What once seemed too ordinary to study may turn out to be one of the East coast’s most overlooked migrations.
Published – November 20, 2025 01:40 pm IST
