Anthropogenic noise and vegetation cover affect the vocalizations of resident Oriental magpie-robins in Kathmandu Valley, Nepal

Urbanization is a major factor accounting for land transformation globally. Kathmandu is now one of the most rapidly urbanizing areas in the world. Urbanization and population growth, in turn, lead to increasing noise pollution that impacts biodiversity in a variety of ways. Anthropogenic noises can cause ‘signal masking’ in bird communities thus creating obstacles in acoustic signals for communication, territorial defense and mate attraction. This study assessed the effects of anthropogenic noise and vegetation cover on the vocalizations (both calls and songs) of the Oriental magpie-robin (OMR) in the Kathmandu Valley. Vocal recordings of OMRs were conducted from September to October 2022 (for calls) and from February to March 2023 (for songs) at randomly selected sites in Kathmandu Valley. The level of anthropogenic noise at the sampling sites also was measured concurrently and ranged between 31.00 and 85.90 dB, with the highest levels observed in the core urban areas. Linear mixed model revealed the number of elements of submissive call decreased whereas the minimum frequency of juvenile calls increased with an increase in noise level. The minimum frequency of OMR songs decreased with the increase in NDVI value. Therefore, to mitigate the impact of noise on bird communication, conservation efforts should focus on reducing noise pollution and enhancing vegetation quality in urban areas.