Vocalization strucure of oriental Magpie-Robin (copsychus saularis Linnacus, 1758) along urbanization gradient in Kathmandu valley Nepal
Date
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Department of Zoology
Abstract
Urbanization is an important factor for global land transformation and Nepal is one of the
most rapidly urbanizing countries in the world. One of the negative impacts of urbanization
and population growth is noise pollution causing various biological responses. Such
anthropogenic noises cause ‘signal masking’ to the bird communities which use acoustic
signals for communication. This creates obstacles for birds for communications, territory
defense and mate attraction. So, this study was carried out to explore the vocal response;
both calls and songs of Oriental Magpie-robin (OMR), along the urbanization gradient of
Kathmandu Valley as it has lower vocal frequencies vulnerable for being masked. Thirtyone
random
sites
were
selected
and
differentiated
into
rural,
suburban
and
urban
based
on
the
Normalized
Difference
Vegetation
Index
(NDVI)
index. The vocal recordings of the
OMR were made from 06:00 a.m. to 11:00 a.m. from September 2022–October 2022 for
calls and February 2023–March 2023 for songs with Zoom H2n recorder and shotgun
microphone. The data were extracted using Raven pro 1.6 software from spectrograms and
analyzed in R Program. The minimum frequency of calls and number of elements were
statistically different along the urbanization gradient. But for the songs, only the maximum
frequency differed statistically. Similarly, the minimum frequency had a statistically
significant positive correlation with anthropogenic noise level, whereas the number of
elements of call had a negative correlation with the same. However, no significant
relationship was observed with other song parameters and anthropogenic noise levels.
Vegetation structure should be increased in urban areas of Kathmandu Valley to reduce the
impacts of noise as vegetation acts as the sound absorbing materials.