Avain Diversity along Urbanization Gradient of Butwal Sub- Metropolitan City, Nepal
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Department of Zoology
Abstract
Global population shift from rural to urban areas intensifies the urbanization which causes
changes in the species composition. Butwal Sub-Metropolitan City in the central lowland
Nepal is also facing the rapid changes in land use and land cover, due to urbanization. In this
regards, this study was undertaken in the Butwal Sub-Metropolitan City aiming to know the
effects of urbanization on avian diversity. The area was categorized as urban and suburban
on the basis of NDVI (Normalized Difference Vegetation Index) value, the median value
taken as the threshold for the demarcation. Altogether, 8 transects (4 in urban and 4 in suburban
areas) each of 2 km length were deployed. Point count stations were positioned at
every 200 m interval along transects. Avian surveys were conducted during the winter and
post monsoon seasons of 2020. The avian community structure in the study area was
characterized. The associations of avian richness and abundance with NDVI as the proxy of
productivity and human footprint data as the proxy of human disturbance were established.
Overall, 69 bird species were recorded from 33 families under 14 orders, where
Passeriformes was the most dominant order, while insectivores was the most dominant
feeding guild. Species richness was higher in winter than in post monsoon. The suburban
sites had higher bird diversity and richness than urban sites. This study also illustrated rural–
urban gradient effect, supporting the intermediate disturbance hypothesis. Vegetative cover
showed positive effects on species richness; on the contrary, human pressure showed
negative effects on bird species richness. Temperature and precipitation influenced the avian
species richness and abundance. This study clearly demonstrates the importance of vegetative
cover and urban greenery for checking the species decline in urban areas, thus, urban policy
makers should focus on increasing green spaces in and around the city.