The recent news of “Bhutan’s first water sports park to be developed along the riverfront in Wangdue” generated a mixed-feeling among some people although the larger group is rather least concerned. While the news conceivably brought a smile on the faces of tourism and business industries; conservationist, birdwatchers and nature lovers couldn’t embrace the news graciously. However, apart from us, there are thousands of others to whom this news essentially is not gratifying and yet have no clue about it. Thousands of birds and other animals take refuge there every winter and has significantly contributed to our pride of being among the top ten-biodiversity hotspots in the world today.

Punatsangchhu valley is one of the 23 Important Bird Areas (IBA) in Bhutan. Whether you are grinning or disheartened by the news, the Punatsangchhu is vividly under pressure. A substantial portion of the river is being defaced by two major hydropower projects and remaining is being ravaged to satisfy our desire. There are still a few last remaining green spots that many admire today.

If you happen to drive from Bajo towards Punakha dzong or vice versa, you will be welcomed with the quacking music of hundreds of reddish ducks in flocks. You will see them in flocks flying, swimming and enjoying their feast in the river or the paddy field. The picture is just like a tropical beach overwhelmed with tourist on annual vacation. And yes, they are Ruddy Shelducks on vacation all the way from southeastern Europe and central Asia.

The less than two-kilometer extent of the river is also a favourite spot for an enthusiast birder, not to listen to the quacking of the ducks but to watch tens of other fascinating species that too have traveled thousands of miles into the valley for the winter. The rare Ibisbill, the near threatened Ferruginous Duck, vulnerable Pallas’s Fish-eagle and critically endangered White-bellied Heron, are some of the target species for the ardent birders, among other wading and shorebirds. The spectacular mandarin duck has also been sighted a few times in the area. Three new bird species (Oriental Pratincole, Whiskered Tern & Common Goldeneye) were also discovered and added to the growing checklist of birds of Bhutan from the area couple of years ago. There are also hundreds of other migratory and resident birds, mammals, fishes and hundreds of other undocumented herpetofauna that make the valley a paradise for nature lover and ecologically one of the most avian biodiverse sites in Bhutan and perhaps among many south Asian countries during this season.

The avian diversity in the valley is seasonal; the migratory behaviour of birds influences what you get in the list. Although migration is a natural tendency across the animal kingdom, it is exceptionally prevalent and ecologically essential in class Aves. It is a complex and life-threatening phenomenon, which again is not uniform throughout all bird species. Studies have shown that some parts of the world have a higher proportion of migrants than others, but at least 4,000 species are known to migrant regularly. It is about 40 percent of more than 10,000 bird species known to science today. Some birds fly thousands of miles back and forth between breeding and non-breeding areas, some migrate regionally, some locally while others stay within a few kilometers from where they are borne.

Why the Punatsangchhu valley matters? The valley is the only wintering habitat to more than 1,500 migrants belonging to more than 50 species apart from hundreds of other resident and sedentary species. It is also home to about 70 percent of waterbird species recorded in Bhutan as per the records of Birds of Bhutan. The wildlife habitats in the valley have shriveled at an exponential rate over the last decade. As a consequence, the population of indicator species like cormorants and ducks is exceedingly decreasing, especially on the lower regions. This has also resulted in surprisingly high species concentration into smaller spaces as we see between Bajo and Khuruthang today. The spot has become extremely crucial for the survival of the 100 plus species and any further alteration of the area will potentially yield a disastrous outcome. The resident and sedentary species will be forced to shift and ascertain a new habitat and deprived of access to resources in the area. This might be apparent for some adaptable species, yet it can be challenging for micro-habitat depended and sensitive one. However, the story could be different for migrants.

Migration is a critical part of the bird’s life cycle yet most challenging. Scientists from the Cornell Lab of Ornithology found that 35 percent of land birds that migrate to US mainland and 23 percent of that migrate to tropics for winter die on their way before reaching back to the summer homes. The rate is potentially higher in other parts of the world. Natural occurrences like harsh weathers cause many deaths, but human activities, like obstruction of migratory route, collusion with buildings, towers and transmission lines and destruction of landing habitats are the primary cause of birds’ untimely demise.

So, why do birds migrate? And why some migrate, and others do not? Several studies conducted in the past proposed that birds migrate as a response to the spatial and temporal distribution of resources and to benefit from a seasonal availability of food. However, a more specific study by Somveille et al., in 2015 found that migration during nonbreeding season is primarily driven by avoidance of harsh winters, site productivity, and connectivity to breeding grounds. On the other hand, birds move to breeding-grounds mainly to take advantage and exploit the surplus in resources, preferring areas with harsh winters, presumably to avoid competition. Answering why some migrate, and others do not? A study led by Doyel et al. in 2011 found that it is partly driven by dietary preferences, where migrants tended to have slightly stronger fruit preferences than residents and also migrants were found to be competitively superior foragers then residents. Since the food supply and weather are alike throughout the year in warmer regions, a fewer number of birds migrate, especially in the tropical environs.

How do they decide where to go? Many birds have a genetic knowledge of the route; they go wherever their ancestors have gone. For some, the flyways get imprinted as they follow their parents; they continue to go wherever their parents took them as a chick and some simply follow flocks to reach a destination. Studies have shown that birds use several mechanisms in combination like landmarks, wind directions, solar cues, stellar cues, geomagnetic cues and some even use the unique olfactory capability to reach their desired destination. Punatsangchhu might be the only imprinted or genetically coded wintering ground for many species and might be the valley that is only ecologically environmentally suitable site for some species like Ibisbill who need glacier feed river systems for survival. Also, some species might be ecologically and biologically restricted to the valley although others might be more flexible. Therefore, if we infringe the last remaining habitats in the valley, that would end the lives of thousands who travel thousands of kilometers only to know that their last remaining home has been devasted. Protection of the last remaining habitats and reclamation of degrading sites is the only solution we have at our capacity to preserve our precious environment and sustain the species diversity.

Today, the valley is one of the most visited tourist destinations; no eco-tourist or bird watchers complete their journey without scanning the picturesque valley. Unfortunately, the iconic species like White-bellied Heron and Ibisbill are disappearing due to an increasing frequency of rafting, picnicking and riverside recreational activities in the area. The rising population of feral dogs is another urgent issue we need to address to ensure the safety of wildlife. Recreating favourable habitats for target species, building professional birding spots, safe bird hide for photographers, researchers and environmental education would contribute to sustainable tourism without dissipating our natural asset.


Contributed by  Indra Acharja


School of Forestry and Environmental Studies, Yale University