- Intense summer heat affected animals in some cities across India, particularly birds, causing dehydration and other heat-associated illnesses.
- Loss of natural habitat and unavailability of food and water due to heat waves and increasing urban spaces affect birds in several ways.
- Besides dehydration, increased heat also affects reproduction and normal feeding behaviour.
- Experts suggest that more research is vital for the conservation of birds, as climate projections indicate rising trends in temperature in the coming years.
India experienced one of its hottest summers in 2024 with temperatures reaching as high as 50°C in some parts of the country. Major cities in India recorded high temperatures; Pune reached 43.3°C, Bengaluru 41.8°C and Hyderabad 44.2°C. At 43°C, Kolkata recorded the highest temperature in nearly 50 years. To manage the heat and its impact on humans, some cities took active measures such as closing schools earlier, providing clean drinking water in public areas, organising public cooling spaces and requesting citizens to stay indoors as much as possible.
The plight of non-human lives, however, remained low on the priority list. Birds, bats, and reptiles, particularly those inhabiting urban spaces, faced severe dehydration and heat-associated illness.
Birds seemed to be particularly affected. In April, there were reports of birds falling from the sky in Mumbai, while in Pune, several birds were admitted into wildlife hospitals and rescue centres, as they battled with dehydration. In Bengaluru, data from People for Animals (PFA), an animal welfare NGO, reveals that over the last three years, there has been an increase in the number of birds affected by dehydration. Speaking of birds, particularly the ones found in cities, Nawaz Shariff, chief veterinarian with PFA, said, “Dehydration cases are now common in species such as black kites, barbets, house crows, jungle crows and Asian koels.”
Cities: The ‘Hot’spots
According to experts, birds face multiple risks associated with increased temperatures, especially in urban spaces which are 1 to 3°C hotter on average than rural spaces as they retain more heat energy due to the urban heat island effect. Increasing urbanisation strips cities of natural spaces and deprives them of their habitat. Further, migratory birds that follow environmental cues can be misguided because of seasonal variations, affecting the existing populations’ behaviour. A 2019 study based on migratory birds in the United States notes the possibility of phenological changes in migratory patterns due to climate change.
Generally, birds expend most of their energy in flying, foraging, and grooming. They have a higher basal metabolic rate and body temperature ranging anywhere between 104 to 106 degrees Fahrenheit (40 to 41 degrees Celsius). Since they have small bodies, they require considerable energy to thermoregulate themselves. If environmental temperatures go beyond their body temperature, birds suffer from dehydration. This results in physiological and behavioural changes in the birds.
“Birds exhibit physical symptoms like weakness, panting, inactivity, sunken eyes, tenting (skin elasticity) and thick mucus deposits near the beak. They also exhibit behavioural changes such as pecking and attacking aggressively, depression, and reduced physical movements like grooming,” says Arun A. Sha, Director, Research and Veterinary Operations at Wildlife SOS.
Although dehydration is a common problem in birds in summer, it can also be a symptom of another underlying cause, not solely heat waves, explains Subiksha Venkatesh, lead rehabilitator at Avian and Reptile Rehabilitation Centre, Bengaluru. She said, “The bird has to be completely free of other ailments for us to classify it as a case of summer dehydration.”
Having said that, she emphasises that the impact of increasing temperatures, due to heat waves and climate change, is borne by birds in more ways than one. “Heat stress is a much more complex process,” she says.
Although dehydration is one of the most common, direct impacts on all living organisms in heat conditions, it also causes depleted quality of nutrition, degradation of habitats, and behavioural adaptations like altered frequency of water and food. Mating rituals and reproductive processes can also undergo disturbances. A study conducted on southern pied babblers (Turdoides bicolor), an endemic species of southern Africa, shows that high air temperature hinders reproductive activity in birds as they showed lower tendencies to visit nests and incubate young clutches. The number of visits they made to drinking water sources varied throughout the day, peaking at noon.
“For most birds, and reptiles too, breeding coincides with the summer,” she says. The eggs and young chicks are more susceptible to the intense heat, thus impacting the birds’ fertility. Birds that nest in open spaces risk the exposure of young chicks to overheating, which suppresses growth.
“In the case of reptiles, a temperature rise can alter the process of sex determination, which then skews their population dynamics,” she explains.
Adapting to heat
To help urban birds cope with the heat, Arun Sha suggests that citizens can implement easy, cost-effective measures like setting up food and water bowls in gardens. “We, as individuals, should be responsible and contribute. Maintenance of natural habitats like water puddles, gardens, and lakes provides them a place to inhabit,” he added. In his opinion, small, territorial birds such as sparrows, parakeets, crows, and finches among others get dehydrated often.
More research could also help with adaptive conservation strategies, according to Anusha Shankar, an assistant professor at the Tata Institute of Fundamental Research, Hyderabad. Now a physiological ecologist, she studied hummingbirds, their energetic strategies and energy budget allocations to changes in physical temperatures. “Based on broad trends of climate and land use change, there is a decline in bird populations. There have to be more studies, particularly in India,” she says.
Climate change projections predict ascending temperature trends in India and across the world. The frequency of heat waves and extreme conditions has risen sharply over the years and is expected to increase in the coming years. Researchers say adaptive measures and conservation efforts are pivotal in addressing population decline in wild species and habitat fragmentation.
The focus on urban wild populations that coexist in this setting plays an important role in safeguarding their survival and the ecosystems that they live in. Birds, particularly, offer ecosystem services such as seed dispersal, pollination and regulation of insect populations. Subiksha believes, “Understanding how our lifestyle and actions impact birds is essential for people to respond firsthand to heat stress, especially if we intend to save them.”
CITATION:
Horton, K. G., La Sorte, F. A., Sheldon, D., Lin, T., Winner, K., Bernstein, G., Maji, S., Hochachka, W. M., & Farnsworth, A. (2019). Phenology of nocturnal avian migration has shifted at the continental scale. Nature Climate Change, 10(1), 63-68. https://doi.org/10.1038/s41558-019-0648-9
Bourne, A. R., Ridley, A. R., McKechnie, A. E., Spottiswoode, C. N., & Cunningham, S. J. (2020). Dehydration risk is associated with reduced nest attendance and hatching success in a cooperatively breeding bird, the southern pied babbler Turdoides bicolor. Conservation Physiology, 9(1). https://doi.org/10.1093/conphys/coab043
Banner image: A bird drinking from a water bowl. Water bowls act as a refuge during dry seasons and heat waves. Image by Frank Cone via Pexels.
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