Impacts of Artificial Lighting on Avian Biodiversity: A Case Study of Udaipur (Rajasthan), India

The pervasive presence of artificial light in urban environments significantly affects biodiversity. This study investigates the impact of light pollution on avian biodiversity in Udaipur, India. Excessive artificial lighting alters natural habitats, disrupts ecosystems, and affects the behaviour and abundance of various avian species. The study was conducted in Udaipur from December 2019 to March 2023, utilizing Visible Infrared Imaging Radiometer Suite (VIIRS) DNB Free Cloud Composite Imagery and field surveys. The research spanned rural and urban landscapes, employing methods such as timed species counts and point counts to assess avian fauna. The Shannon-Wiener Diversity Index was used to measure biodiversity, with ANOVA and Tukey’s post-hoc tests for statistical analysis. VIIRS data analysis revealed three light pollution clusters: dark, moderately dark, and bright areas. Avian diversity varied across these clusters, with significantly higher diversity observed in dark areas. Daytime and night time observations also showed variations, with higher biodiversity observed at night. Common species exhibited significantly higher abundance in brighter areas, while moderately dark and dark areas supported greater diversity. Artificial lighting has profound effects on avian biodiversity in Udaipur. Bright areas exhibit reduced biodiversity, while dark areas support richer ecosystems. This study underscores the importance of managing light pollution to preserve avian diversity and maintain ecological balance in urban environments.


Introduction
Since light is ubiquitous on our planet, it is apparently linked to the life of all biota and it would be therefore expected, that excess lighting would impact all life-forms.Studies carried out by different workers have supported this assumption.Today the night skies in the cities are hundred times brighter than that in nature therefore, it is difficult to see the stars and other celestial bodies in a brightly lit city.Changes in ambient temperature due to heat dissipated from excessive lighting can bring about subtle environmental changes with more profound long-term consequences.Another aspect of these environmental changes is an increase in the production of greenhouse gases, which are considered responsible for profound environmental degradation.Light pollution entails wastage of energy, since a large part of energy (electricity) production involves burning of fossil fuels, it leads to the addition of greenhouse gases (e.g., carbon dioxide) to the environment without serving any useful purpose.Thus, greenhouse gas production runs parallels to light pollution as serious light pollution may also potentially contribute directly to greenhouse pollution by raising ambient temperatures locally.
Light pollution makes nighttime look like daytime, which can drastically impact nocturnal animals.Light pollution may adversely affect the survival of a particular species in a food chain and indirectly impact the survival of another species that feeds on it, thus disturbing the ecological balance of that area [1] [2] .Analogous consequences would result if artificial lighting creates an environment conducive to better survival and breeding of a species.Predators use light to hunt, and darkness is a safety cover for the prey [3][4] .A range of behavioral changes have been attributed to light pollution in different animals, e.g., attraction of moths to artificial light at night; the moths attract bats, in turn.Many moths are eaten up by bats, and some get killed by the heat of the light source.Thus, light pollution has the potential to decrease the population of moths and increase that of bats.Migratory birds are known to be disoriented by bright lights, and light pollution may make them migrate too early or too late, so that they may miss the ideal time for nesting and other breeding behavior, affecting their population [5][6] [7] .Advanced onset of dawn song has been reported in songbirds due to light pollution [8] .Light pollution has led sea-turtle hatchlings to migrate away from the sea and consequently die, resulting in a serious drop in the population of this species [9][10] [11][12] [13] .Amphibian inhabitants of wetlands indulge in nighttime croaking -a breeding ritual to attract their mates.Light pollution inhibits this behavior, and the amphibians are not able to breed normally, leading to a decline in their population [14][15] [16] .On a larger scale, the species-specific changes may also alter community dynamics and even the ecological balance of the area.Excessive artificial lighting has been suggested to be responsible for disturbing delicate ecological balances and environmental parameters.Light pollution in the form of sky glow, glare, clutter, and light trespass has adversely impacted the environment [17] .Other types of pollution, like dust and smoke, may amplify light pollution by light scattering.The most obvious effect of light pollution is sky glow, which obscures our view of the true night sky.
The present study explores the relationship between light pollution and avian diversity, considering birds as bioindicators of ecosystem health.By employing transect surveys and biodiversity indices, the research seeks to elucidate how varying levels of artificial light impact the abundance, richness, and composition of avian communities in different urban settings.Furthermore, the investigation delves into the potential interactions between light pollution and species-specific traits, such as habitat preferences and activity patterns.Understanding how different species respond to artificial light is crucial for designing effective conservation strategies and mitigating the negative impacts of light pollution on biodiversity.
Overall, this study contributes in giving valuable insights of the complex interplay between urbanization, light pollution, and biodiversity conservation.By elucidating the ecological consequences of excessive artificial lighting, the resultant findings can be used in policy-making, urban planning, and environmental management practices aimed at promoting sustainable coexistence between human activities and natural ecosystems.

Materials and Methods
Study Area: The study was conducted in Udaipur city, situated within the Aravalli Range of mountains in the state of Rajasthan, western India.Udaipur is renowned for its natural and man-made lakes, earning it the epithet "City of Lakes." The study area encompasses both the historic "Walled City" and the contemporary "Outer City," each with distinct characteristics and urban layouts.

Data Collection Period:
The research spanned from December 2019 to March 2023, totalling to 40 months.Data was presented for 39 months, excluding July 2022 due to data unavailability.The study period coincided with the COVID-19 pandemic, during which a lockdown was imposed, affecting data collection procedures.The total lockdown duration was 68 days, during which field recordings were collected during designated relaxation hours from 7:00 pm to 10:00 pm.
VIIRS Data Collection: VIIRS-DNB Free Cloud Composite Imagery, obtained from the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA), was utilized for light pollution analysis.Filtering techniques were applied to selected images to remove short-term events, with image processing methods used to distinguish stationary illumination from transient sources.

Study Limitations:
Limitations of the study include data unavailability for July 2022 and the impact of the COVID-19 lockdown on data collection efforts.Additionally, the coarse spatial resolution and limited dynamic range of satellite imagery may have affected the accuracy of light pollution assessments.

VIIRS Studies
The      Effect of light on bird diversity with reference to their abundance There were significant differences in mean bright area observations across the three abundance levels of the species (Common, Moderately common or Less common) (p = 0.000).Post-hoc tests showed common species abundance had significantly higher mean bright area observations compared to moderately dark common and less common abundance levels.There was no significant difference between moderately common and not-common abundance levels.
There were significant differences in mean moderately dark area observations across abundance levels (p = 0.001).Posthoc tests showed common abundance had significantly higher mean moderate observations compared to moderately common and less common.There was no significant difference between moderately common and not-common.
There were significant differences in mean dark area observations across abundance levels (p = 0.002).Post-hoc tests showed common abundance had significantly higher mean dark observations compared to moderately common and less common.There was no significant difference between moderately common and less common.Effect of light on bird diversity with reference to their habit The analysis of variance (ANOVA) was conducted on habitat types-diurnal, nocturnal, and both-across different brightness areas.For the Bright Area, while the between-groups comparison yielded an F-value of 2.25, suggesting some difference between habitat types, the p-value of 0.116 was not significant.Similarly, for the moderately dark area, the between-groups F-value was 3.03 with a p-value of 0.058.The dark area displayed a similar trend, with an F-value of 2.92 and a p-value of 0.06.Subsequent Tukey's post-hoc tests aimed to discern specific differences between habitat types.
While some pairwise comparisons revealed notable mean differences, the associated p-values were non-significant.

Sum of
data was divided into 3 clusters (k=3).The percentage of variance explained by the clustering solution with k=3 is 86.98%.This indicates how well the clusters represent the variability in the data.The SSE (total variance within each cluster) is 128.2248.The SSG (the variance between the cluster centroids) is 856.4728.The SST (total variance in the data) is 984.6977.The centroids (centers) of the clusters are given as 5.69 (dark area), 17.984 (moderately dark area), and 25.71 (bright area) respectively.These represent the average values of the data points within each cluster along each dimension.

Figure 2 .
Figure 2. K-value Clusters as observed for VIIRS Values

Figure 3 .
Figure 3. Violin Plot Representing Avian Diversity Observed in Bright, Moderately Dark and Dark Area

Figure 4 .
Figure 4. Violin Plot Representing Avian Diversity Observed During the Night and Day Time Excess kurtosis and Outliers.The Avian diversity during the study period was measured using the Shannon-Wiener Diversity Index.Data were further subjected to ANOVA and followed by Multiple Comparisons (Tukey's Posthoc) to assess the significance level.All the data was analysed using Microsoft Excel.

Table 3 .
Analysis of Variance (ANOVA) Results for comparison of VIIRS Value Between Bright Area, Moderately Dark Area and Dark Area Results indicate that there is a statistically significant difference among the VIIRS radiance (F(2, 17) = 428.407,p < 0.001) across the clusters, as the F value is 56.785 with a very low p-value of.000,suggesting strong evidence against the null hypothesis of equal means.Diversity Studies with reference to effect of light Descriptive statistics for all three groups revealed the minimum values for all three groups (Bright, Moderately Dark and Dark Area) are 1, and the lower boundaries are -28.375 for Bright Area, -26.5 for Moderately Dark Area, and -15.75 for Dark Area.The Q1 values are 2 for Bright Area, 2 for Moderately Dark Area, and 3 for Dark Area.The medians are 8 for Bright Area, 7 for Moderately Dark Area, and 8 for Dark Area.The Q3 values are 22.25 for Bright Area, 21 for Moderately Dark Area, and 15.5 for Dark Area.The upper boundaries are 52.625 for Bright Area, 49.5 for Moderately Dark Area, and 34.25 for Dark Area.The maximum values are 60 for Bright Area, 58 for Moderately Dark Area, and 57 for Dark Area.The IQR values are 20.25 for Bright Area, 19 for Moderately Dark Area, and 12.5 for Dark Area.The mean values are 14.7568 for Bright Area, 13.5682 for Moderately Dark Area, and 13.5 for Dark Area.The skewness values are 1.5204 for Bright Area, 1.5219 for Moderately Dark Area, and 1.7593 for Dark Area, indicating asymmetrical and right/positive skewness for all three groups.The excess kurtosis values are 1.5324 for Bright Area, 1.5921 for Moderately Dark Area, and 2.2576 for Dark Area, indicating leptokurtic distributions with long heavy tails for all three groups.The outliers for Bright Area are 59, 58, and 60, for Moderately Dark Area are 52, 53, and 58, and for Dark Area are 49, 39, 55, 55, and 57.

Table 5 .
Analysis of Variance (ANOVA) Results for Species Abundance (Common,

Table 7 .
ANOVA Analysis of Habitat Preference Among Diurnal, Nocturnal, and Both time active Species