Has climate change hit migration of birds?

winged visitors: Bar-headed geese fly with the Himalayas in the background. In 2018, their number was 34,883 — down from 52,530 in 2017. (below) Pong reservoir in Himachal Pradesh. Sankara Subramanian via flickr/author

As teenagers in the 1980s, Tilak Raj and Santosh Kumar, locals of Nagrota Surian near Dharamsala in Himachal Pradesh, used to see the vast expanse of the Pong reservoirs teeming with birds in the winter. Four decades down the line, Raj and Kumar, who currently earn their bread as fishermen, don’t see some of the species that used to touch down at Pong at the onset of winter and have also noticed a drop in the overall number of birds.

Located in Kangra district, Pong is one of the largest man-made wetlands in North India formed by the construction of a giant dam across the Beas river in 1974. This is the first major wetland that offers a transitory resting reserve for migratory birds coming from the trans-Himalayan zone in the winter when the wetlands in Europe and North and Central Asia are frozen. Between October and March every year, flocks of waterfowls that breed in those areas in the summer migrate to Pong and other Indian wetlands to spend winter in more congenial climatic conditions.

Over the years, the vast reservoir has witnessed a slow decline in the number of these winged visitors. Earlier this year, Himachal Pradesh Chief Minister Jairam Thakur informed the Assembly that the total bird population observed at Pong in 2018 was 1.10 lakh, down from the 2017 count of 1.27 lakh. The next counting is expected in January 2019.

Bird census

A look at the bird census data of the last five years shows that 2014 was the best year in terms of the number of species (119 species) whereas 2015 recorded a bird count of 1.35 lakh, highest in the last five years. Since then, the number of species has dropped below 100 for three consecutive years before returning to 117 in 2018. The individual count is going down steadily since 2015. The best bird year happened almost a decade ago when the count touched the 1.5 lakh mark.

Is this decline due to a change in weather patterns? While the opinion is divided owing to the absence of scientific studies, scientists and forest department officials haven't completely rule out the impacts of climate change on the hill state.

“In 2018, the bird count was less in Pong and other wetlands in North India possibly because of warmer climate. According to the Wetland International, an organisation that carries out water bird estimation in important wetlands, the reason was climate change,” Krishan Kumar, divisional forest officer (DFO), Hamirpur who is in-charge of Pong, told DH.

Another forest official, however, differed. “There is no systematic study to link the bird count with changing weather. The varying bird numbers at Pong is linked more to the water dynamics of the reservoir. But we have seen the impacts of changing climate on local birds like pheasants that have moved upwards,” said D S Dhadwal, DFO-Headquarters (Wildlife Circle) at Dharamshala.

Concurs R Suresh Kumar, a scientist at the Wildlife Institute of India, who studies birds. “If there is warming, birds will come later and if the winter approaches fast then birds will arrive faster. But it is time that we should start systematically looking at the link between climate change and migratory bird behaviour,” he said.

A beginning has been made through a Department of Science and Technology-funded project to look into the impacts of climate change on the resident species of the Himalayas. “We are setting up the baseline for bigger studies,” said Kumar.

Over the last decade, several groups abroad have looked into the correlation between climate change and migration of birds. Migratory species require suitable conditions throughout their annual cycle — in their breeding grounds, in their non-breeding range, and along migratory routes between the two. Climate change has the potential to disrupt conditions in all three stages.

In a study by British scientists on European birds and published in a Royal Society Journal in July 2018, the findings showed that birds suffer higher mortality during migration. This is because of increased risk of predation and starvation that result from higher energetic requirements and unpredictable food supplies.

“Longer journey increases these risks, and may, therefore, lead to population decline. Our study provides further evidence that long-distance migrants may be hit particularly hard by climate change,” said Stuart Butchart, chief scientist at BirdLife International and one of the authors of the paper published in Bird Conservation International.

Signature species

One of the signature species in Pong are the bar-headed geese that spend the summer in Central Asia and visit India and other parts of South Asia in the winters. Their number in Pong used to constitute nearly 40% of the world's population, making Kangra wetland the largest single congregation destination for bar-headed geese in the world.

“Pong is also important for bar-headed geese on their return flight from peninsular India, including wetlands in Bengaluru. They are among the highest flying birds crossing over the Himalayas to breed in Tibet and Mongolia. Pong is the last resting site for them,” said Kumar.

In 2018, their number was 34,883 — nearly 18,000 less than the previous year’s count of 52,530. “We need to keep an eye on signature species like bar-headed geese,” Kumar said.

Common pochard, northern pintail, brahminy shelduck, northern shoveller are among other common species that flock to Pong in winter. The number of avian fauna increased by nearly four times in winter, shows an August 2018 study by the Zoological Survey of India’s Solan unit in Himachal Pradesh.

For birds coming from outside India, Pong provides the first pit stop after which the winged creatures disperse to sites like Bharatpur and Bhopal. “For them, Pong dam is a funneling site, conservation of which is absolutely essential for the movement of migratory birds,” Kumar said.

Kumar is part of a five-member team that in August came up with India’s first National Action Plan for Conservation of Migratory Birds and their Habitats along the Central Asian Flyway (CAF) in the next five years. It flags the importance of protecting the 40-odd wetlands and wetland clusters for the sake of migratory birds and Pong — one of the Ramsar sites in India — is among them.

The Central Asian Flyway, one of the nine flyways in the world, encompasses overlapping migration routes over 30 countries for different waterbirds linking their northern most breeding grounds in Russia (Siberia) to the southernmost wintering grounds in West and South Asia.

India has a strategic role in the flyway, as it provides critical stopover sites to over 90% of the bird species known to use this migratory route. At least 370 species of migratory birds from three flyways (CAF, East Asian Australasian Flyway, covering parts of eastern India, and Asian East African Flyway, covering parts of western India) visit the Indian subcontinent, of which 310 predominantly use wetlands as habitats, the rest being land birds.

Long-term data shows a declining trend in migratory land bird population mainly because of change in land use and climate change. Pong has several other wetland management issues that need to be addressed by the officials from the two states to improve the birding experience. But with a long-running court case between Punjab and Himachal Pradesh concerning Pong, this is easier said than done.

(The report is being published as part of GIZ-CMS Media Fellowship programme)

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Has climate change hit migration of birds?

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