Honey Bee Swarm Seasonality

Using David Marshall's (MABA’s swarm commander) 2022-2023 Atlanta swarm records I created a histogram graph with eight bins. The raw data has many of days with no swarms and combining two years in a simple graph does not completely patch days with no swarms days or sufficiently smooth the data. The histogram peaks on March 28 ± 10.5 days, and then there is a long tail into the summer months. 

I discovered a paper, Seasonal Cycle of Swarming in Honeybees, that combined six years of Ithaca, NY swarm emergence dates - I digitized the paper’s Figure 1A.  I created a histogram plot with nine bins. Figure 1A and the resulting histogram graph show a bimodal seasonal pattern – peaking on June 9 ± 7.5 days with a smaller peak in the summer months. 

 

 

I exchanged emails with one of the authors, Thomas Seeley, and shared how spring frost and fall frost climate data might reconcile these Atlanta and Ithaca swarm peaks. 

• The Ithaca x-axis contains fewer days than the Atlanta y-axis and is consistent with Ithaca's shorter growing season.
• In Atlanta and Ithaca, the peak swarm (orange circle) appeared before the local last spring frost.

I’ll leave it to the readers why honey bees in Atlanta don’t have a smaller summer peak like Ithaca – I don’t know. Having a pattern bias has sometimes served me well in making quick decisions, detecting missing data, or spotting corrupted data - what the typical swarm season pattern should look like is still up for grabs!