Bumblebee flower constancy and pollen diversity over time

Bees often focus their foraging effort on a few or even a single flower species, even if other equally rewarding flower species are present. Although this phenomenon – called flower constancy – has been widely documented during single foraging trips, it is largely unknown if the behavior persists over longer time periods, especially under field conditions with large spatial and temporal variation of resources. We investigated the pollen diet of individuals from nine different Bombus terrestris colonies up to six weeks, placed at either 0, 300 or 1000 m from nearest autumn sown oilseed rape. Adjacency to oilseed rape affected constancy, with a higher flower constancy in colonies far from fields. Overall, 23 % of the pollen foraging trips were flower constant, and the fraction of constant pollen loads did not change over time, although repeatedly sampled individuals that were flower constant once often showed different preferences at other sampling occasions, and the similarity between po...