Why doesn't nectar robbing decrease seed set in some bee-pollinated plants?

Abstract

Unlike hummingbird-pollinated plants, some bee-pollinated species do not suffer reproductive loss by nectar robbing. This observational study investigated the probability that Bombus sp forage on either Mertensia ciliata or Corydalis caseana legitimately at least once before bees rob the flowers. I bagged flowers and waited two days. On the day of the experiment, I monitored the uncovered flowers and voice- record bumblebee visits and type (legitimate vs. robbing).