<p>Urbanization poses novel ecological challenges for animals, often driving morphological and behavioral changes. In this study, I investigated risk-taking behavior, measured as flight initiation distance (FID), in seven bird species inhabiting both highly urbanized areas of Tokyo and rural areas of Ibaraki Prefecture, Japan. All species exhibited significantly shorter FIDs in urban habitats, indicating increased tolerance toward human approach. Effect sizes (Hedges' <i>g</i>) for FID differences between urban and rural habitats were larger than those previously reported from Europe, suggesting more pronounced behavioral shifts in Tokyo, likely driven by the city's exceptionally high human population density. No clear correlation was found between the time since urban colonization and the magnitude of behavioral change, implying that reduced risk avoidance may emerge rapidly via habituation rather than long-term genetic adaptation. This study shows that birds inhabiting the megacity of Tokyo provide a valuable model for investigating change in risk-taking behavior in urban environments, and highlights the need for future studies examining a greater number of species with varying colonization histories and for long-term studies of the same species over time.</p>