Prairie and edge habitats provide valuable nesting resources for bumble bees (Bombus) in the midwestern U.S.

Abstract Bumble bees use three main habitats to complete their life cycle: foraging habitat, overwintering habitat, and nesting habitat. Overall, the majority of bumble bee research has focused on the foraging habitat and flower preferences of bumble bees, leaving a large knowledge gap regarding nesting and overwintering habitats. These aspects of the bumble bee life cycle are notoriously difficult to observe, and the time required to locate such locations is often considered prohibitive, leaving them to be largely understudied. This lack of information on the nesting habitat requirements of bumble bees also has negative consequences regarding conservation action. Here, we set out to determine the nesting habitat preferences in a rigorous, standardized fashion. In 2022 and 2023, we conducted standardized surveys for nesting bumble bees to assess habitat preferences in forest, prairie, and edge habitats. We surveyed 21 plots for a total of 168 person hours per habitat type (63 plots, 504 h total) at sites along the St. Croix National Scenic Riverway in Minnesota and Wisconsin, USA. We found a total of 25 nests of 6 different bumble bee species. Bumble bee nests were more likely to occur in prairie and edge habitats than in forest habitat. The results of this study indicate the importance of prairie and edge habitats for nesting bumble bees. Furthermore, results from this study are useful for informing management of bumble bee nesting habitat and further developing protocol for finding bumble bee nests more efficiently.