Guwahati: A study has recorded eight owl species across Guwahati, identifying ambient noise as a major factor affecting researchers’ ability to detect the nocturnal birds in the city.
The research, published in the journal Urban Ecosystems under Springer Nature, found that owls were recorded in 24 of the 33 one-square-kilometre grid cells surveyed between November 2023 and July 2025. The Barn Owl and Spotted Owlet were the most frequently detected species.
Researchers found that rising ambient noise reduced the likelihood of detecting owls during field surveys. They cautioned that failing to hear or spot an owl does not necessarily mean the species is absent from a particular location.
The study was conducted by Debangini Roy, Shubhankar Khangar and Dr Pankaj Koparde of MIT World Peace University, Pune, under the Urban Owl Project, India.
Barn Owl and Spotted Owlet dominate sightings
The research team surveyed built-up neighbourhoods, vegetated areas, water bodies, agricultural land and wastelands across Guwahati. Researchers used visual observations and acoustic surveys, visiting each selected grid eight times across four seasonal periods.
Of the eight species recorded, only the Barn Owl and Spotted Owlet were detected frequently enough for detailed analysis of their occupancy patterns. The other six species were the Brown Hawk Owl, Brown Fish Owl, Collared Scops Owl, Mountain Scops Owl, Oriental Scops Owl and Asian Barred Owlet.
The researchers estimated the baseline occupancy of the owl community at 84%. However, detection rates varied across locations and seasons.
The probability of detecting a Barn Owl was estimated at around 3.4%, while the corresponding figure for the Spotted Owlet was approximately 12%.
These findings highlight the challenges of monitoring nocturnal birds in an urban environment, where background sounds can mask their calls.
Urban noise affects owl detection
Ambient noise emerged as the most consistent factor associated with reduced owl detection across the study’s statistical models. Traffic intensity also lowered detection probability in some analyses, while weather conditions affected recordings during certain seasons.
Debangini Roy, who led the field surveys, said the city’s soundscape was one of the biggest challenges during late-night observations.
“An owl might be calling or perched just a few meters away, but vehicular traffic and background urban hum easily drown out their vocal activity,” Roy said.
She added that failing to spot an owl during a survey did not necessarily indicate that the area lacked the birds. In some cases, urban noise could simply prevent researchers from detecting their presence.
Urban expansion reshapes owl habitats
Guwahati’s landscape includes densely built-up neighbourhoods, green spaces, wetlands and forest patches. However, rapid urban expansion has significantly altered the city’s land use.
The study cited earlier research indicating that built-up land in Guwahati more than doubled between 1990 and 2020, largely replacing vegetation, fallow land and wetlands.
Researchers found that Barn Owls and Spotted Owlets continued to occupy different parts of the urban landscape. However, links between owl occupancy and individual habitat features were less consistent than the relationship between noise and detection.
Barn Owl occupancy showed a positive association with under-construction sites in the multi-season analysis. Other associations varied across seasons and involved features such as flowering trees, factories and warehouses.
The authors said these findings suggested that some owl species could tolerate modified urban environments. However, the results did not establish clear preferences for particular habitats.
Researchers call for noise-sensitive urban planning
Owls can be difficult to monitor because they are active at night and often remain undetected during conventional bird surveys. The study emphasised that researchers must account for detection probability when assessing the presence of nocturnal species.
The authors recommended conserving remaining vegetation and green spaces, maintaining a variety of habitats and considering noise pollution in urban planning. They also called for long-term monitoring programmes that account for the possibility of missing species during field surveys.
Dr Pankaj Koparde, co-author of the study and assistant professor at MIT World Peace University, Pune, highlighted the ecological role of owls in urban environments.
He said nocturnal predators provide important ecological services, including natural rodent control in densely populated areas.
Koparde argued that urban development should go beyond planting ornamental roadside trees and prioritise the protection of remaining green patches and mature trees with natural cavities. He warned that noise pollution and habitat fragmentation could drive away these predators and disrupt natural pest regulation across the city.
The researchers acknowledged that the study covered a limited number of grid cells. They said future assessments could benefit from additional information on prey abundance and more detailed measurements of artificial lighting.