Monitoring free-living honeybee colonies in Germany: Insights into habitat preferences, survival rates, and Citizen Science reliability

Abstract

Our understanding of the western honeybee (Apis mellifera) predominantly stems from studies conducted within beekeeping environments, leaving the presence and characteristics of honeybees outside managed settings largely unexplored. This study examined the habitats, nesting sites, and survival rates of free-living colonies through personal monitoring of nest sites in Munich (N=107) and the coordination of Citizen Science monitoring across Germany (N=423). Within seven years we collected 2,555 observations on 530 colonies from 311 participants. Nesting preferences differed between urban, rural, and forested areas. Overall, we found that 31% of the occupied nest sites were in buildings and 63% in mature trees, with clear preferences for specific tree species. On average, only 12% of the personal monitored colonies in Munich survived annually, a figure that aligns well with other published studies but contrasts sharply with the significantly higher survival rates reported by Citizen Science (29%). We found that Citizen Science yielded significantly fewer updates per colony, underreported abandoned sites, and that 46% of overwintering reports overlapped with the swarming season and had to be excluded. To gain reliable survival data in Citizen Science projects, consistency and timing of reports need particular attention and regional swarming should be monitored too. This study enhances our understanding of the ecological dynamics, liminal state, and conservation needs of free-living honeybee cohorts, addresses potential monitoring biases, and suggests standardized data collection protocols for future monitoring projects.