Swarmed Predictive Model: Daily and Seasonal Swarm Likelihood
Version 1.0
Prepared May 2025
Introduction
Swarming is a natural reproductive behavior of honey bee colonies (Apis mellifera), usually occurring in the spring. It represents a critical point of colony expansion and environmental interaction. Swarmed.org, the global swarm reporting and rescue network, maintains a growing database of over 10,000 historical swarm reports. To better serve beekeepers, we have developed a weather-driven model to predict the daily likelihood of swarming in a user-defined area, as well as the seasonal swarm pressure curve month-by-month.
This whitepaper documents version 1.0 of the Swarmed Swarm Likelihood Model. It describes the environmental science underpinning swarming, the model’s reasoning, data sources, scoring mechanics, and future directions.
Objective
• Predict daily swarm likelihood (score 0–100) based on current weather conditions and seasonal progression
• Predict month-by-month swarm pressure for a given region using historical swarm data (under development)
• Make predictions location-specific, based on the radius defined by each beekeeper
Scientific Background
Swarming behavior is influenced by both internal colony factors and external environmental conditions. For the purposes of this model, we focus only on external, observable environmental variables, as these can be retrieved or forecast programmatically.
Key Drivers of Swarming (Environmental Focus):
Temperature: Swarms typically occur when daytime temperatures are warm and nights are mild. Swarming is rare below 12°C and peaks in the 16–28°C range.
Precipitation: Bees do not swarm during rainfall. However, rain delays can build up pressure, leading to increased swarming once the weather clears.
Multi-day Warming Trends: Gradual warming over several days can signal optimal conditions and often precedes swarming spikes.
Wind Conditions: Calm to moderate wind (<20 km/h) is favorable; high winds suppress flight.