Pollen is a highly profitable resource for bees for their survival and reproduction. Previous studies show that bumblebee colonies found at least 2 km apart, forage for pollen from its surrounding resources. However, if there are multiple bumblebee colonies within a less than 2 km radius area, they should share pollen resources in some ways. In this study, we examine pollen choices of natural bumblebee colonies found in a small spatial habitat and investigate factors affecting their pollen choices. We analyzed the pollen compositions of seven Bombus ardens colonies found within 2.5 x 2.5 km area. We mapped floral patches visited by B. ardens queens and workers in the study area. Observed pollen choices of the seven colonies showed great variation. This variation can be caused by the following two factors; 1) small scale segregation of pollen resources among the colonies, to minimize traveling cost of pollen foraging 2) an artifact of colony size differences because larger colonies would show wider pollen repertories. Our analyses showed the above two factors cannot fully explain the observed variation patterns of pollen choices, and we discuss other possibilities for explaining the differences in pollen usage.