Urbanization alters ecosystems through multiple biotic and abiotic changes that directly affect urban biodiversity. However, we still lack information on how urban areas influence the ecosystem services provided by wildlife, particularly regulating ecosystem services (RES) such as seed dispersal, pollination, pest control, and scavenging. Recent studies have shown marked differences in animal communities depending on urban landscape configuration, which ranges from land-sharing (low-density housing with small, fragmented green areas) to land-sparing (high-density housing with large, unfragmented green areas). Because this gradient affects animal communities, we expect it to also influence potential ecosystem service provision. In addition, several local urban attributes may influence these communities and, consequently, could also affect RES provision. To address these research questions and their potential temporal variation, we collected bird assemblage data from nine European cities during the breeding and non-breeding seasons. We used bird diets and abundances to identify the main species providers of the four avian-mediated RES mentioned above and analyzed their variation in potential service provision along the urban landscape organization gradient. Land-sharing areas provided higher potential scavenging (both seasons), seed dispersal (non-breeding), and pest control (non-breeding). Several urban attributes (e.g., abundance of fleshy fruit-bearing plants) significantly enhanced RES, while others (e.g., built cover) reduced them, although these effects varied seasonally. These findings provide new insights into the debate on how cities can be more biodiversity-friendly and can help to implement measures based on local urban attributes that promote RES provision, both of which are vital for urban ecosystems and citizens’ well-being.