Urbanization enhances the breeding performance but does not affect the reproductive success of Chinese Blackbird (Turdus mandarinus)

Urbanization provides novel habitats for bird species, while simultaneously posing numerous threats to them. Although several bird species have successfully adapted to urbanization, the underlying adaptation mechanisms of reproductive success remain poorly understood in rapidly urbanizing areas. To this aim, a total of 168 breeding pairs of the Chinese Blackbird ( Turdus mandarinus ) were monitored during the breeding season (March–July) from 2018 to 2023. We used environmental factors (including nest tree variables, and concealment variables), phenotypic characteristics of nestlings, number of nest predation events, and quantified urbanization scores to understand the impact of urbanization on breeding performance of Chinese Blackbirds. In our study, generalized linear models and structural equation modeling showed that Chinese Blackbirds tended to initiate laying earlier and lay eggs with larger volume along an increasing urbanization gradient. We also found that urbanization did not affect the growth condition of nestlings, and the predation risk was lower in more urbanized habitats. Most importantly, urbanization did not have negative consequences on the reproductive success of Chinese Blackbirds. Our results show changes in the breeding behavior of Chinese Blackbirds as they adapt to rapid urbanization and suggest that certain more urbanized areas may be suitable for the breeding of bird populations.