- Rapid urbanization in Nepal’s capital, Kathmandu, has led to changes in bird behavior, with urban birds showing increased tolerance toward humans.
- The urban sprawl has caused habitat loss, with the city’s built-up area expanding by 112% between 1989 and 2019, largely at the expense of open green spaces and trees crucial for bird nesting.
- Birds such as the house crow have adapted by using urban materials, such as wires and human clothes, for nesting, while other species have become scarce or disappeared entirely from urban areas.
- Despite government efforts, researchers highlight the need for more native trees in urban areas to preserve bird habitats and promote biodiversity.
KATHMANDU — Birds living in Nepal’s capital may be losing their fear of humans in response to rapid unplanned urbanization — with potential ramifications for the diversity of birdlife in the Kathmandu Valley, two recently published studies indicate.
Both studies show that city birds are increasingly becoming tolerant to human presence in the rapidly expanding urban sprawl devoid of trees (let alone native ones), suggesting that some generalist species may proliferate massively while more specialist species may lose out and eventually disappear.
“The results of the studies are positive if you look at it through the lens of human-bird coexistence,” researcher Kamal Raj Gosai, who wasn’t involved in either of the studies, told Mongabay. “However, one of the many downsides to this is that native birds that can’t live close to humans may find it hard to survive.”
Kathmandu lies in a valley that was once an ancient lake. In recent decades, the city has witnessed unprecedented growth in its built-up area, primarily at the expense of its green spaces and trees.
Between 1989 and 2019, the urban built-up area expanded by 112% to 189.2 square kilometers (73.1 square miles). It’s projected the built-up area in the Kathmandu Valley will continue to grow to 301 km2 (116 mi2) by 2030 and 352 km2 (136 mi2) by 2050.
Nepal’s parliament recently passed a nationwide land-use law, but it hasn’t been implemented yet in the capital. Here, residents can build houses on any plot of land they own, regardless of its suitability. As real estate prices skyrocket, many residents can’t afford large plots, resulting in fragmented holdings with barely enough space for a house, let alone for trees where birds can build their nests or source building materials from.
Some birds, such as the house crow (Corvus splendens), have thrived amid this change. A recently published study led by Dinesh Bhusal, a forestry researcher at Kathmandu’s Tribhuvan University, found that crows were the most abundant nesting birds in the valley. They not only used nonnative trees such as avocado for nesting, but also electricity lines and poles, using materials such as wires and human clothes as building materials.
A ring road encircling Kathmandu divides the city’s core from its “lesser-developed” surroundings. Outside the ring road, settlements are relatively new, population density is lower, and people have bigger land holdings compared to inside the core area.
This difference is often used by bird researchers to compare how birds behave in urban and rural settings in Kathmandu. However, with plans to expand the ring road, areas outside the ring road could become homogenized with those inside in terms of average land holding and numbers of buildings and trees.
The study by Bhusal and his team supports Gosai’s hypothesis that urbanization may have led to the displacement of some birds unable to adapt to the rapid changes. Bhusal and his team found that despite being located in similar geographical terrain, rural settings were home to more species of birds compared to urban ones.
The authors of the study note that with the exception of four species, all the birds recorded in urban sites were also recorded in rural sites. However, rural sites boasted 31 species not recorded in urban sites.
Several species of birds such as spiny babblers (Acanthoptila nipalensis), peregrine falcons (Falco peregrinus) and various vultures have become rarer in the valley in recent decades. Some researchers such as Gosai say they believe these species’ displacement could be linked to their inability to adapt to changing habitats and rapid urbanization.
Not only have the successfully adapted birds such as crows changed their behavior with regard to nesting, they’ve also become increasingly tolerant to human presence. That’s according to a study led by Amrit Nepali, a zoologist at Tribhuvan, comparing the fleeing response between rural and urban birds.
Known as the flight initiation distance (FID), this measures the minimum distance at which birds flee when approached by humans or predators. It’s often regarded as a proxy for measuring bird tolerance to humans. Nepali and his team found a lower FID for urban birds compared to rural birds, meaning urban birds are less sensitive to human presence than their rural counterparts. People in urban areas often feed birds around parks and temples, which might be perceived by birds as non-threatening, enhancing acclimatization and reducing fear of humans.
“At first glance, we could say that this is good for the urban birds as it helps in their long-term survival,” said Hem Bahadur Katuwal, a co-author on the FID study. “But this also means that, just like humans, birds are also losing their connection with nature and their natural instincts and way of life.”
Another worry is about the stress levels in urban birds. Nepali, lead author of the FID study, said that because urban birds live close to humans, they need to remain on alert mode for a longer period of time, which could increase their stress hormones, impacting their reproductive success. “For example, when they see food, they need to land next to it and take off as soon as possible to avoid possible encounters with humans,” he said.
Gosai said the close proximity between humans and birds could also result in the transmission of zoonotic disease. “I personally have seen one of my relatives get diagnosed with an allergy related to pigeons living in his terrace,” he said, adding that a buffer is needed in urban environments to maintain some kind of separation between birds and humans. Pigeons, another type of bird that has adapted successfully to human presence, have been found to be infected with various parasites. A 2018 study found heavy gastrointestinal parasite infection in pigeons at two temples in the valley: 90% of the 120 fecal samples collected for the study had either protozoa or parasitic worms. The study authors recommended that action be taken to control the infection and keep the pigeons healthy.
Patches of green and trees, especially of native varieties, however small they be, can provide such a buffer, the study led by Bhusal suggests. It found that as the number of trees increases, the abundance and diversity of birds in urban areas increases much more sharply than in rural areas. This underscores the importance of trees in supporting bird populations, particularly in urban settings where natural habitats aren’t available, the authors of the study note.
The national and local governments have in the past announced several programs to improve the greenery of the city. However, these programs haven’t been effective, a result of lack of political will and stringent enforcement. Similarly, there’s a growing trend among city dwellers to cultivate nonnative tree species such as avocado, which research shows doesn’t support nesting of native birds.
Bhusal said his team’s study emphasizes the importance of trees for birds and humans, so it’s now up to the municipal authorities to take the issue seriously and do something about it.
Banner image: Tourists interact with birds at the Bouddhanath shrine in Kathmandu. Image by Abhaya Raj Joshi
Abhaya Raj Joshi is a staff writer for Nepal at Mongabay. Find him on Twitter @arj272.
Citations:
Bhusal, D., Ghimire, P., Low, M., Rosin, Z. M., & Timilsina, Y. P. (2024). The diversity and nesting preferences of birds along an urban-rural gradient in the Kathmandu Valley, Nepal. Urban Ecosystems, 28(1), 1-13. doi:10.1007/s11252-024-01631-0
Nepali, A., Katuwal, H. B., Kc, S., Regmi, S., & Sharma, H. P. (2024). Flight initiation distance and bird tolerance to humans in rural and urban habitats. Royal Society Open Science, 11(10). doi:10.1098/rsos.240332
Gurung, A., & Subedi, J. R. (2018). Prevalence of gastrointestinal parasites of pigeons (Columba sp. Linnaeus, 1758) in three temples of Pokhara Valley, Nepal. Journal of Natural History Museum, 30, 287-293. doi:10.3126/jnhm.v30i0.27604
In Kathmandu, when the falcon’s away, pigeons come out to play. And poop