Season, Microclimate and Shoreline Disturbance Interactively Shape Bird Functional Diversity

Abstract

Understanding how ecological processes shape avian community structures remains fundamental to conservation in tropical coastal ecosystems, where birds serve crucial roles as seed dispersers, scavengers, and prey population regulators. West African coastal habitats face mounting pressures from urbanization and changing microclimate; however, we lack a comprehensive understanding of how these stressors interact with seasonal cycles to influence functional diversity. We examined how seasonality, microclimate, and shoreline disturbance shape bird functional diversity along a 15 km coastal transect in Ghana's Central Region. Bird communities were surveyed across the dry and wet seasons at 30 points. Four functional diversity indices (Functional Richness, Evenness, Divergence, and Dispersion) were quantified using trait-based approaches. Multivariate analyses demonstrated that the interaction between the shoreline condition and season significantly influenced trait composition (PERMANOVA: R2 = 0.045, p < 0.001), with natural shorelines exhibiting pronounced seasonal functional turnover that was suppressed in urbanized sites. Natural shorelines showed higher functional dispersion during the dry season (4.01 ± 0.29) than the wet season (1.90 ± 0.16), whereas urbanized shorelines maintained stability year-round, dominated by generalists, including Pied Crow (Corvus albus) and Yellow-billed Kite (Milvus aegyptius). Functional divergence increased from the dry to wet seasons (0.877–0.901), while functional richness was higher during the wet seasons (6.72 vs. 5.29). Cloud cover was the most consistent environmental predictor, negatively associated with functional dispersion (β = −0.012, p < 0.001) but positively associated with divergence (β = 0.004, p < 0.01). Air temperature β = 0.316, p < 0.001 and low tidal levels (β = 0.318, p < 0.05) positively influenced dispersion. These findings demonstrate that urbanization dampens the temporal dynamics essential for ecosystem resilience, emphasizing the need to preserve natural shoreline integrity for maintaining seasonal functional turnover in tropical coastal regions.