Pollen preferences of honey bees: how do floral and pollen characteristics influence foraging strategies?

Background: Understanding honey bee pollen foraging behavior is crucial for optimizing pollination services in agricultural systems. Floral and pollen characteristics significantly influence pollinator preferences and foraging efficiency. Aim: This study investigated the influence of floral characteristics and pollen traits on the foraging preferences of the honey bee (Apis mellifera ligustica) in Australian cotton agroecosystems. Methods: In summer 2007, pollen traps were installed on eight honey bee colonies adjacent to cotton fields. Collected pollen pellets were analyzed for their weight, color, and botanical origin. Scanning Electron Microscopy was used to examine pollen morphology and size. Statistical analyses included Pearson’s correlation and analysis of variance with Tukey’s HSD test. Results: Honey bees showed significant preferences for specific pollen sources (F₇,₂₈ = 84.593, p < 0.02). Acacia concurrens was the most collected species (37.4%), followed by Maireana villosa (17.5%) and Helianthus annuus (13.3%). Cotton (Gossypium hirsutum) contributed only 5.3% of the total pollen. A strong negative correlation was found between pollen grain size and pellet weight (r = −0.89, p < 0.05). Smaller, smooth-textured grains (e.g., M. villosa, 31 μm) produced heavier pellets (6.42 mg), whereas larger grains (e.g., G. hirsutum, 101 μm) produced lighter pellets (2.45 mg). Brightly colored flowers (yellow and orange) were strongly preferred over creamy white blossoms. Conclusion: Honey bees optimize foraging by selecting flowers with favorable morphology, vibrant colors, and collectible pollen traits. The low preference for cotton pollen despite its abundance highlights the importance of alternative floral resources for maintaining honey bee colonies in agricultural landscapes. These findings provide a foundational understanding of the ecology of pollen foraging, the principles of which remain relevant for informing current strategies to support pollinator health and crop pollination services in agricultural landscapes.