Urbanization induced by human activities presents both challenges and adaptive opportunities for wildlife. One notable impact of urban sprawl is the vast amount of waste it produces, which has discernible effects on wildlife. Interestingly, an emerging trend has been observed that birds are incorporating anthropogenic materials into their nests. However, the relationship between anthropogenic nesting materials (ANMs) and the reproductive performance of urban birds is unclear. In this study, we investigated the relationship between the incorporation of ANMs into nests and the reproductive performance of Chinese Bulbuls (Pycnonotus sinensis) by monitoring and collecting data on 136 breeding nests in Hangzhou, China. We gathered data on seven reproductive traits of Chinese Bulbuls, including laying date, incubation period, nestling period, clutch size, egg volume, hatching success rate, and fledging success rate. We then calculated the urbanization synthetic index as a measure of the level of urbanization and examined its relationship with the proportion and weight of ANMs. Through examination of nest components, we observed significant increase in the proportion and weight of ANMs with the urbanization synthetic index. Notably, we found a higher hatching success rate of Chinese Bulbuls with an increasing proportion of ANMs. However, the inclusion of ANMs in nests was not correlated with other reproductive traits of Chinese Bulbuls. Overall, the use of ANMs by Chinese Bulbuls is consistent with the adaptive hypothesis and the availability hypothesis. Further studies should use controlled experiments to investigate the impact of ANMs on avian reproductive success.

Urbanization brings new selection pressures to wildlife living in cities, and changes in the life-history traits of urban species can reflect their responses to such pressures. To date, most of the studies investigating the impacts of urbanization on avian life-history traits are conducted in Europe and North America, while such studies are often lacking in quickly developing countries in Asia (e.g., China). In this study, we examined the variations in reproductive life-history traits of Chinese Bulbuls (Pycnonotus sinensis) along the urbanization gradient in Hangzhou, China. We detected 234 natural nests of Chinese Bulbuls and continuously monitored them in two continuous breeding seasons from 2012 to 2013. We collected data on seven life-history traits (laying date, incubation period, nestling period, clutch size, egg volume, hatching success rate, and fledging success rate). We used infrared cameras to record the number of feedings per hour as the measure of food resources for the nestlings. We measured nest predation pressure by monitoring 148 natural breeding nests during breeding seasons and 54 artificial nests immediately after breeding seasons. We then calculated the urbanization synthetic index (USI) as a measure of the level of urbanization and examined its relationship with the seven life-history traits. We found that Chinese Bulbuls laid eggs significantly earlier with increasing USI. However, the other six life-history traits did not vary significantly with the USI. Moreover, the feeding frequency of chicks increased significantly with the USI, but the nest predation pressure of Chinese Bulbuls decreased significantly with the USI. Increased food resources and reduced nest predation pressure in cities may lead to earlier laying date of Chinese Bulbuls. Further study should test whether the earlier laying date of Chinese Bulbuls is the result of phenotypic plasticity or genetic change.