Complementarity and Ecological Structure of Method-Exclusive Bird Detections from Observer-Based and Automated Monitoring in an Urban Botanical Garden

Urban biodiversity monitoring increasingly combines field surveys with automated technologies, but species detected by only one approach may represent ecologically structured subsets rather than random omissions. We integrated 2025 bird records from monthly observer-based transect surveys, autonomous acoustic monitoring, and infrared camera traps in Shanghai Botanical Garden, China. Annual presence–absence data were analyzed without comparing absolute monitoring efficiency. Manual surveys detected 112 wild bird species and multi-source automated monitoring detected 101; 83 species were shared, 29 were manual-only, and 18 were automated-only, yielding 130 species in total (Jaccard = 0.638). In a multivariable logistic model with joint detection as the outcome, resident status was positively associated with joint detection (adjusted OR = 7.76, 95% CI = 1.71–35.19, p = 0.008), whereas regional rarity in Shanghai was negatively associated with joint detection (adjusted OR = 0.287, 95% CI = 0.113–0.728, p = 0.009). These associations show that method-exclusive detections under the 2025 protocols were non-random with respect to residency and regional commonness, although unequal temporal coverage limits causal interpretation. Periodic observer-based surveys, continuous acoustic monitoring, image-based evidence, and expert validation provide complementary components of long-term urban bird monitoring.