Escape behaviors of the Eurasian Tree Sparrow (Passer montanus) across China: Northern populations are bolder than southern populations

Abstract

Urbanization has significantly altered the habitat structure and behavioral patterns of animals. In urban environments with frequent human disturbances, animals may undergo adaptive adjustments in their escape behaviors. This study focuses on Eurasian Tree Sparrows (Passer montanus) from five cities across different latitudes in China, comparing their flight initiation distance (FID) in urban and rural areas to assess the impact of urbanization on their escape behavior and the trend of ecological homogenization. The results confirm the established pattern at the geographic level: a reduction of FID in urban habitats and a decrease in FID with increasing latitude. That is, northern populations of the Eurasian Tree Sparrow in China are bolder than the southern populations. In addition, FID is positively correlated with flock size, with rural flocks exhibiting more pronounced group behavior (observed flocking frequency for urban and rural is 28.74% vs. 40.7%, flock size variance is 26.90 vs. 55.63). Despite the differences between northern and southern latitudes, the variability of FID in urban individuals consistently remains lower than that in rural areas, supporting the trend of reduced variability in escape behavior among birds in urban environments. Driven by urbanization, the escape behavior of Eurasian Tree Sparrows tends toward ecological homogenization, meaning that behavioral differences between urban areas in different cities are diminishing. This trend may obscure the behavioral variability brought about by latitude gradients, indicating that urbanization not only shapes the behavioral adaptations of birds but also potentially weakens their behavioral diversity.