Come winter and bird enthusiasts like me get excited. It’s the season when migratory birds arrive in our part of the world. Lakhs of birds flock from Europe, Russia, Mongolia and Central Asia and other distant lands to descend at our parks, gardens, wetlands and water bodies. Even in urban areas like Kolkata, it’s a mesmerising sight to watch the Eurasian wryneck, Siberian Rubythroat, Bluethroat and Desert Wheatear forage alongside the local resident birds for a brief period, enriching the avian diversity of our locality.
To imagine that a bird foraging in your backyard could have been in Europe or Siberia some time back, is indeed thrilling! And considering the challenges some of these migratory birds encounter along their arduous migratory routes make them even more admirable. For instance Bar-headed geese fly over the frozen Himalayas when the temperature can freeze exposed flesh as they make their astonishing high-altitude migration to wintering grounds in India. Long-distance migrants like the Little Stint, a small wader bird that covers roughly 11,000 km, flying all the way from the Arctic to winter here.
The exciting migratory season begins around September-October when migratory birds start arriving, our diverse landscapes and climate conditions making the country a suitable wintering ground for a variety of species who spend the winter here and head homeward the following spring. Every year along with the usual seasonal visitors, a few new species pique our interests. This year has been no different. Among the 3.5 lakh migratory birds that include Greylag Geese, Pochards, Mallards, Gharwals, Common tails and Pintails to arrive at the lakes and wetlands of Kashmir, the Whooper Swan has been sighted at Hokersar wetland. At Odisha’s Chilika lagoon, the largest wintering site of our country, the Mongolian gull has been sighted this year along with over a million birds recorded here.
Birds unable to adapt to the elements of weather migrate to avoid the harsh conditions of colder regions. As daylight period becomes shorter and the supply of food at their breeding sites begins to get scarcer, birds know it’s time to make the long journey, mostly at night guided by celestial bodies. They follow regular flyways to ensure proper refuelling and rest. The wintering sites these birds choose depend on their specific needs like suitable nesting and feeding grounds which mostly include wetlands, grasslands, forests and water bodies. Over the years these wintering sites become their favourite haunts and for bird enthusiasts, conservationists and researchers who record census and study migratory patterns of birds, they know where they can find a specific species.
Since these birds return year-after-year some of these wintering sites begin to be identified with specific avian visitors. Like Pulicat Lake spanning across parts of Tamil Nadu and Andhra Pradesh is popular for the Greater Flamingo, so is Nal Sarovar Bird Sanctuary in Gujarat. Chilika is significant for geese, gulls, terns and ducks. Some years back the critically endangered Siberian Crane wintered at Bharatpur Keoladeo National Park. Similarly Purbasthali of West Bengal with its wetland and agricultural fields make it possible to sustain a healthy mix of migratory species as well as resident birds and is immensely popular with birdwatchers looking to get a glimpse of the beautiful Red-crested Pochard. Such lakes and reserves are not only tourist hotspots and prime attractions for birdwatchers who seek to enjoy the enormous bird diversity, they also attract poachers. It has been seen in the past that an effective way to stop poaching is to involve the local community in the conservation plan to protect the biodiversity of their locality. Such sensitization has not only led to decrease in poaching, the residents have become active agents of conservation.
While migratory birds are a delight for bird lovers they also have ecological importance and their role as pest control and seed dispersal agents contribute significantly to maintain biodiversity of the ecosystems they transverse through as well as the wintering grounds they inhabit. The record of the number of migratory birds in a particular region is also an indicator of the health of surrounding environment and impact of climate change in that particular place. For instance, this year the increase in number of migratory birds at Santragachi Jheel in West Bengal indicates better health of the water body and has been a reason for celebration among bird enthusiasts and conservationists.
There is a close correlation between climate change and migratory species distribution over a particular region. Since temperature change can directly impact the food source migratory species depend upon, birds often find themselves out of sync with these elements of the ecosystem when they arrive. Also, with erratic season changes it becomes difficult for birds to recognise the cues and to properly time their migration. What makes migratory birds even more vulnerable is that they might alter their timing of migration, but the plants and organisms they rely on for sustenance at their breeding and wintering sites, for that matter even stop-over sites, do not do so. The stress migratory birds face was highlighted in the global status report on Bird Species and Climate Change in 2006 which raised an alarm and pointed to shrinking habitats and change in bird behaviour as a cause for concern. The threat was further recognized by the International Union for Conservation of Nature and two years later they warned of catastrophic consequences which could lead to the extinction of one in eight bird species in the future.
Since migratory birds travel the world to be with us it’s only befitting that like perfect hosts we ensure their safety and protect their wintering and stop-over sites, besides being responsible birdwatchers and not disturb them when they roost or during breeding periods.