Urbanization Reduces the Nest Size of Barn Swallow ( Hirundo rustica ) in South Korea

Urbanization affects the natural world, with implications for habitat availability and wildlife behavior, notably in the context of South Korea. This study investigates the effects of urbanization on the nest sizes and materials of barn swallows, a migratory bird species. Utilizing comparative analyses across suburban, exurban, and rural regions, the study found substantial variations in nest volumes. Specifically, rural areas had significantly larger nests than suburban areas, whereas exurban nest sizes fell in between. Although a potential explanation might relate to differences in the availability of nesting materials, this hypothesis necessitates further investigation. The study also found that the soil composition in nests varied by location, with sand, silt, and clay content showing marginal differences, but not statistically significant disparities. However, a clear preference for a specific soil texture was evident, along with the finding that forest cover within a 1 km radius of the nest was correlated with larger nest sizes. Land use was further linked to the external volume of barn swallow nests, pointing to a potential interaction between habitat quality and nest construction. Overall, the findings underscore the complexity of urbanization’s impact on barn swallows, emphasizing the need to conserve natural habitats and devise strategies to mitigate the negative effects on these birds. These results contribute to the growing understanding of urban ecology and the urgent need for thoughtful management of human-altered landscapes.