Climate-driven synchronization of honey bee flight activity and plant phenology in Türkiye: development of a Beekeeping Climate Suitability Index (BCSI)

Honey bees (Apis mellifera L.) provide essential pollination services that depend on the temporal synchronization between flight activity and plant flowering phenology, both strongly influenced by climatic conditions. However, this relationship remains insufficiently quantified at large spatial and temporal scales. In this study, we quantified climate-driven honey bee flight activity and its alignment with flowering phenology of major nectar plants in Türkiye using ERA5-Land data for the period 1981–2023. Suitable flight days were defined based on temperature (≥12°C) and precipitation (0 mm), and seasonal suitability was evaluated at a monthly scale. A composite Beekeeping Climate Suitability Index (BCSI) was developed by integrating flight activity, flowering overlap and nectar flow window. The number of suitable flight periods ranged between 4 and 7 months (mean ≈5.5), indicating substantial interannual variability. Flight flowering synchrony was low for early-spring species (23–35%) but reached 100% for summer species. BCSI values ranged from 0.44 to 1.00, capturing variability in climatic suitability for beekeeping. These findings demonstrate that climatic variability plays a decisive role in shaping bee plant interactions and provide a quantitative basis for climate-informed beekeeping management.