Balancing energy efficiency and avian conservation: divergent nest-site selection responses of Barn Swallows and Red-rumped Swallows to attached sunspaces in cold rural landscapes

Human-modified landscapes serve as ecological filters, determining species distributions and persistence. Energy-efficient technologies, while crucial for climate change mitigation, represent novel filters whose impacts on synanthropic biodiversity are poorly understood. We investigated how attached sunspaces, a widely adopted energy-saving technology in rural China, filter the distribution of two ecologically important aerial insectivores, the Barn Swallow (Hirundo rustica) and Red-rumped Swallow (Cecropis daurica). We surveyed 106 villages during the 2024 and 2025 breeding seasons and recorded a total of 2323 nests (612 Barn Swallow, 1711 Red-rumped Swallow). Using Generalized Linear Models, we assessed their responses to building characteristics, landscape composition and the prevalence of sunspaces. Barn Swallow nests preferred perches at the base and single attachment faces, while Red-rumped Swallow nests favored multiple attachment faces and avoided long shelters. The proportion of buildings with sunspaces acted as a strong positive filter for Barn Swallow nest abundance (+24%) but as a significant negative filter for Red-rumped Swallow (−51%). Other landscape variables (e.g., human population density, NDVI, Human Footprint Index) were not significant. This study demonstrates that specific architectural innovations can act as powerful ecological filters, leading to divergent distributional outcomes for sympatric species reliant on anthropogenic structures. Our findings reveal a critical trade-off in sustainable development: energy efficiency gains may inadvertently reduce habitat suitability for certain species. To reconcile climate and biodiversity goals in rural landscapes, we advocate integrating species-specific habitat requirements into building design. We propose actionable modifications to sunspaces to support swallows without compromising energy savings. These principles provide a template for mitigating the distributional impacts of green infrastructure globally.