The foraging behavior of a native pollinator, Bombus vosnesenskii (Radoszkowski) (Hymenoptera: Apidae), in flowering red clover

While honey bees have provided pollination services for a diversity of crops, two mite species and the recent colony collapse have reduced their availability. This has increased dependence on native bee pollinators but limited information is available regarding their foraging efficiencies. This study was conducted to examine the foraging behavior of native bumble bees in red clover seed production fields in Oregon, where producers typically stock honey bee hives for pollination. The study addressed the following: 1) Are native bumble bee and managed honey bee pollen-collecting foragers equal in number? 2) Does the foraging behavior of native bumble bees vary with colony size? The bumble bee species used in this study was Bombus vosnesenskii. For comparing bumble bees with honey bees, counts of bee foragers were made during two-minute visual observations through red clover bloom. The results indicated temporal differences as honey bees were greater in abundance early in the season (p=0.01), while bumble bees were more abundant late in the season (p=0.004) with a larger proportion observed carrying pollen (p=0.04). To determine the impact of colony size, individual bumble bee workers from large and small colonies were marked and observed during peak foraging periods. Data analyses suggest considerable variation in frequency and duration of foraging trips. Observations of marked workers in adjacent red clover fields provided additional insights on distances traveled from the nest. These data will be presented, and the potential use of B. vosnesenskii for pollination of red clover for seed will be discussed.