citizen science - free-living bees

I’ve been poking around the internet for the next interesting journal article. This month, I typed citizen science + honeybee into Google Scholar, and one paper really stood out: “Monitoring free-living honeybee colonies in Germany: Insights into habitat preferences, survival rates, and citizen science reliability.”  The study compares research-grade observations of free-living honeybee colonies around Munich (N=107), with observations from a much larger citizen science project across Germany (N=423). Where possible, the authors aim to combine high-quality research data with citizen science observations to expand the geographic scope of the study. 

Free-living honeybee takeaways

• 63% of colonies nest in large-diameter, mature trees
• 31% nest in buildings

Why survival was overestimated
Colonies monitored directly by researchers in Munich showed only about 12% overwinter survival. Citizen scientists reported much higher survival (around 29%), but this turned out to be biased due to fewer follow-up reports and poorly timed observations.
Many “surviving” colonies reported by volunteers were actually new swarms discovered early in the season (46% overlapped with the swarming period).
Abandoned nest sites were often not reported, making colonies appear longer-lived than they really were.

Cavity entrance direction: buildings vs. trees
Radar plots show that:

• Tree cavities have a strong preference for south-facing entrances (20%)
• Building cavities show a preference for west (22%) and south (16%)

Cavity entrance height: buildings vs. trees

• Median entrance height for tree cavities: 4 meters (13.1 ft)
• Median entrance height for building cavities: 6 meters (19.7 ft)

Big-picture takeaway
What are your swarm trap plans for 2026? Will they look like unused bee equipment stacked on blocks, or purpose-built swarm traps raised and baited with pheromones? Does this study change how you’ll deploy your traps?  When building and tree cavity entrance direction are combined, even an unlikely north-facing entrance appeared about 10% of the time. In other words, it’s surprisingly hard to get this wrong. From a next-door homeowner’s perspective, having a swarm-trap plan—any plan—is far better than having none at all.