Objective Creating bird-friendly urban green spaces is a tangible step toward fulfilling the national biodiversity conservation strategy and has gained attention in urban greening efforts. Developing standardized principles and core guidelines for these spaces can help guide construction of green spaces across different areas. Nonetheless, there is limited research on what should be incorporated into guidelines for building bird-friendly green spaces.

Methods Focusing on the principles and content of the guidelines for building bird-friendly green spaces, this study used a literature review to summarize patterns of avian diversity in urban green spaces and their influencing factors. It then examined the resources birds need for survival and the risks they face in these environments. Based on the analysis, essential principles and a content checklist for guideline development have been proposed. The checklist was used to analyze the contents of relevant standards, technical guides, and guidelines to identify their strengths and weaknesses. Additionally, aspects requiring attention in future efforts to develop guidelines were suggested.

Results Urbanization has altered bird diversity in cities both spatially and temporally, shaping overall patterns such as distribution along urban-rural gradients, species composition, and abundance of urban birds. These patterns are mainly driven by environmental filtering and human activities. Habitat changes and pollution—air, light, water, noise—filter urban birds, while human persecution and the introduction of new species select for those adapted to city life. Because bird diversity in urban green spaces is influenced by various factors across different scales, scale-based planning and management are crucial for creating effective bird habitats in green spaces. A truly bird-friendly urban green space must provide essential resources like food, water, shelter, and nesting sites, while reducing risks from light and noise pollution, domestic cats, and human disturbance. Guidelines should be based on core principles that provide overall direction, evaluate reasonableness, and adapt to unforeseen circumstances. Recognizing that making urban green spaces bird-friendly is a multidisciplinary conservation effort, five principles are proposed. 1) Multi-scale planning and design. 2) Prioritizing protection over new construction. 3) Considering species-specific traits. 4) balancing resource provision and risk management. 5) Offering multiple ecosystem services. Building on these principles, a checklist with 28 items covering city, district, and site scales is presented to guide the development and assessment of green spaces. Comparing existing guidelines to the checklist shows that all include site-scale construction techniques, indicating a focus on detailed project guidance. Several guidelines also address district-scale measures, with some extending to city-scale considerations, reflecting a move towards systematic, multi-scale planning to enhance urban bird diversity. All guidelines mention the design and post-implementation phases, but few detail the implementation process itself. Explicit impact mitigation during construction remains underdeveloped. At the city scale, existing guidelines focus on urban planning, goal setting, zoning, and artificial facilities but lack comprehensive surveys and community participation. High technical and resource demands limit city-wide bird surveys, resulting in little data on urban bird diversity, no quantitative indicators or timeframes in overall goals. Guidelines rarely promote community involvement, viewing bird-friendly green spaces more as landscape projects than as conservation efforts. At the district level, focus is on hubs, corridors, and stepping stones, but few address matrix planning, which is vital as ecological corridors depend on surrounding land, especially since birds move through the matrix daily. Planting trees and creating green spaces can improve permeability and reduce population isolation in the matrix. At the site level, guidelines clearly cover site selection, surveys, habitat design, and monitoring, but are less specific on threat analysis, risk management, and post-implementation actions. Few address surrounding buildings, lighting, or construction management, which are crucial because they influence bird behavior and safety. Emphasizing habitat resources while neglecting artificial factors may increase collision risks as habitat quality improves. Variations also exist in detailed methods, such as target species identification—ranging from vague survey-based identification to detailed taxonomic analysis—affecting conservation efforts and evaluations. Most guidelines focus on bird conservation; only one also considers ecological and visual value and human-bird interactions, which could foster local support and sustainability. Based on the above analysis, future efforts in developing new guidelines or revising existing ones should focus on: 1) Risk management—reducing bird collisions, controlling stray cats, regulating lighting and feeding behaviors to prevent ecological traps; 2) minimizing construction impacts on native species; and 3) engaging communities throughout all phases—from species selection and design to monitoring and enforcement—to ensure long-term conservation involvement.

Conclusion The fundamental principles and content checklist outlined in this research are derived from a synthesis of existing knowledge, primarily intended to serve as a reference for developing guidelines related to bird-friendly green spaces. They provide a structured framework to support the development of guidelines for bird-friendly urban green space, thereby advancing the field. Future research may include monitoring and evaluation data from post-implementation assessments of bird-friendly green spaces across different regions to continually update and refine the principles and checklist presented in this study.